'manual kill engaged' during offboard

I’m working on swarm flight with ROS in wifi condition
and sometimes there comes msg ‘manual kill engaged’ and copter crashes (of course I didn`t engaged)
what could be gone wrong?

here are my logs and I’m using ch8 (seems to be 7 in log) for offboard

2017_04_10_07_25_01: DISARMED by RC
2017_04_10_07_27_57: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_27_58: REJECT OFFBOARD
2017_04_10_07_27_59: Already landed, not executing RTL
2017_04_10_07_28_00: RTL: completed, landed
2017_04_10_07_28_00: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_28_01: MANUAL KILL SWITCH OFF
2017_04_10_07_28_01: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_28_01: MANUAL KILL SWITCH OFF
2017_04_10_07_28_01: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_28_01: MANUAL KILL SWITCH OFF
2017_04_10_07_28_01: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_28_01: MANUAL KILL SWITCH OFF
2017_04_10_07_28_34: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_28_55: MANUAL KILL SWITCH OFF
2017_04_10_07_29_03: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_29_10: MANUAL KILL SWITCH OFF
2017_04_10_07_29_12: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_29_12: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_29_14: REJECT OFFBOARD
2017_04_10_07_29_15: Already landed, not executing RTL
2017_04_10_07_29_15: RTL: completed, landed
2017_04_10_07_29_16: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_29_16: MANUAL KILL SWITCH OFF
2017_04_10_07_29_16: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_29_16: MANUAL KILL SWITCH OFF
2017_04_10_07_29_16: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_29_16: MANUAL KILL SWITCH OFF
2017_04_10_07_29_16: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_29_17: MANUAL KILL SWITCH OFF
2017_04_10_07_29_17: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_29_17: MANUAL KILL SWITCH OFF
2017_04_10_07_29_56: PREFLIGHT ADVICE: ACCEL SENSORS INCONSISTENT - CH
2017_04_10_07_29_57: ARMED by arm/disarm component command
2017_04_10_07_29_57: Takeoff detected
2017_04_10_07_29_57: [blackbox] /fs/microsd/log/2017-04-10
2017_04_10_07_29_57: [blackbox] recording: 07_29_56.px4log
2017_04_10_07_31_09: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_09: MANUAL KILL SWITCH OFF
2017_04_10_07_31_12: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_13: MANUAL KILL SWITCH OFF
2017_04_10_07_31_17: no rc
2017_04_10_07_31_17: failsafe mode on
2017_04_10_07_31_17: failsafe mode off
2017_04_10_07_31_22: RTL: climb to 14 m (10 m above home)
2017_04_10_07_31_25: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_25: MANUAL KILL SWITCH OFF
2017_04_10_07_31_25: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_25: MANUAL KILL SWITCH OFF
2017_04_10_07_31_25: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_26: MANUAL KILL SWITCH OFF
2017_04_10_07_31_26: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_26: MANUAL KILL SWITCH OFF
2017_04_10_07_31_26: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_26: MANUAL KILL SWITCH OFF
2017_04_10_07_31_27: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_27: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_27: MANUAL KILL SWITCH OFF
2017_04_10_07_31_27: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_27: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_27: MANUAL KILL SWITCH OFF
2017_04_10_07_31_27: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_28: MANUAL KILL SWITCH OFF
2017_04_10_07_31_28: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_28: MANUAL KILL SWITCH OFF
2017_04_10_07_31_28: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_28: MANUAL KILL SWITCH OFF
2017_04_10_07_31_28: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_28: MANUAL KILL SWITCH OFF
2017_04_10_07_31_29: MANUAL KILL SWITCH OFF
2017_04_10_07_31_29: MANUAL KILL SWITCH OFF
2017_04_10_07_31_29: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_29: MANUAL KILL SWITCH OFF
2017_04_10_07_31_29: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_29: MANUAL KILL SWITCH OFF
2017_04_10_07_31_29: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_30: MANUAL KILL SWITCH OFF
2017_04_10_07_31_30: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_30: MANUAL KILL SWITCH OFF
2017_04_10_07_31_30: MANUAL KILL SWITCH OFF
2017_04_10_07_31_30: MANUAL KILL SWITCH OFF
2017_04_10_07_31_30: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_30: MANUAL KILL SWITCH OFF
2017_04_10_07_31_31: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_31: MANUAL KILL SWITCH OFF
2017_04_10_07_31_31: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_31: MANUAL KILL SWITCH OFF
2017_04_10_07_31_31: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_31: MANUAL KILL SWITCH OFF
2017_04_10_07_31_32: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_32: MANUAL KILL SWITCH OFF
2017_04_10_07_31_32: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_32: MANUAL KILL SWITCH OFF
2017_04_10_07_31_32: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_32: MANUAL KILL SWITCH OFF
2017_04_10_07_31_33: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_33: MANUAL KILL SWITCH OFF
2017_04_10_07_31_33: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_33: MANUAL KILL SWITCH OFF
2017_04_10_07_31_33: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_33: MANUAL KILL SWITCH OFF
2017_04_10_07_31_34: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_34: MANUAL KILL SWITCH OFF
2017_04_10_07_31_34: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_34: MANUAL KILL SWITCH OFF
2017_04_10_07_31_34: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_35: MANUAL KILL SWITCH OFF
2017_04_10_07_31_35: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_35: MANUAL KILL SWITCH OFF
2017_04_10_07_31_35: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_35: MANUAL KILL SWITCH OFF
2017_04_10_07_31_35: MANUAL KILL SWITCH OFF
2017_04_10_07_31_35: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_36: MANUAL KILL SWITCH OFF
2017_04_10_07_31_36: MANUAL KILL SWITCH OFF
2017_04_10_07_31_36: MANUAL KILL SWITCH OFF
2017_04_10_07_31_36: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_36: MANUAL KILL SWITCH OFF
2017_04_10_07_31_36: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_36: MANUAL KILL SWITCH OFF
2017_04_10_07_31_37: no rc
2017_04_10_07_31_37: failsafe mode on
2017_04_10_07_31_38: failsafe mode off
2017_04_10_07_31_38: no rc
2017_04_10_07_31_38: failsafe mode on
2017_04_10_07_31_39: failsafe mode off
2017_04_10_07_31_40: no rc
2017_04_10_07_31_40: failsafe mode on
2017_04_10_07_31_40: failsafe mode off
2017_04_10_07_31_43: no rc
2017_04_10_07_31_44: failsafe mode on
2017_04_10_07_31_44: failsafe mode off
2017_04_10_07_31_45: RTL: climb to 14 m (10 m above home)
2017_04_10_07_31_45: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_46: MANUAL KILL SWITCH OFF
2017_04_10_07_31_46: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_46: MANUAL KILL SWITCH OFF
2017_04_10_07_31_49: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_31_50: RTL: climb to 14 m (10 m above home)
2017_04_10_07_31_51: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_51: MANUAL KILL SWITCH OFF
2017_04_10_07_31_51: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_51: MANUAL KILL SWITCH OFF
2017_04_10_07_31_53: Landing detected
2017_04_10_07_31_55: DISARMED by auto disarm on land
2017_04_10_07_31_55: PREFLIGHT ADVICE: ACCEL SENSORS INCONSISTENT - CH
2017_04_10_07_31_55: ARMED by set mode command
2017_04_10_07_31_55: Takeoff detected
2017_04_10_07_31_57: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_31_58: RTL: return at 4 m (0 m above home)
2017_04_10_07_31_58: RTL: descend to 4 m (0 m above home)
2017_04_10_07_31_58: RTL: land at home
2017_04_10_07_31_58: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_31_58: MANUAL KILL SWITCH OFF
2017_04_10_07_32_00: Landing detected
2017_04_10_07_32_00: Takeoff detected
2017_04_10_07_32_04: no rc
2017_04_10_07_32_04: failsafe mode on
2017_04_10_07_32_05: failsafe mode off
2017_04_10_07_32_05: RTL: return at 4 m (0 m above home)
2017_04_10_07_32_05: RTL: descend to 4 m (0 m above home)
2017_04_10_07_32_05: RTL: land at home
2017_04_10_07_32_05: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_32_05: MANUAL KILL SWITCH OFF
2017_04_10_07_32_06: no rc
2017_04_10_07_32_06: failsafe mode on
2017_04_10_07_32_06: failsafe mode off
2017_04_10_07_32_08: no rc
2017_04_10_07_32_08: failsafe mode on
2017_04_10_07_32_08: failsafe mode off
2017_04_10_07_32_11: no rc
2017_04_10_07_32_11: failsafe mode on
2017_04_10_07_32_11: failsafe mode off
2017_04_10_07_32_11: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_32_12: RTL: return at 4 m (0 m above home)
2017_04_10_07_32_12: RTL: descend to 4 m (0 m above home)
2017_04_10_07_32_12: RTL: land at home
2017_04_10_07_32_12: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_32_12: MANUAL KILL SWITCH OFF
2017_04_10_07_32_13: no rc
2017_04_10_07_32_13: failsafe mode on
2017_04_10_07_32_13: failsafe mode off
2017_04_10_07_32_14: no rc
2017_04_10_07_32_14: failsafe mode on
2017_04_10_07_32_16: failsafe mode off
2017_04_10_07_32_17: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_32_17: REJECT OFFBOARD
2017_04_10_07_32_18: RTL: return at 4 m (0 m above home)
2017_04_10_07_32_19: RTL: descend to 4 m (0 m above home)
2017_04_10_07_32_19: RTL: land at home
2017_04_10_07_32_19: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_32_19: MANUAL KILL SWITCH OFF
2017_04_10_07_32_19: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_32_19: MANUAL KILL SWITCH OFF
2017_04_10_07_32_21: Landing detected
2017_04_10_07_32_23: DISARMED by auto disarm on land
2017_04_10_07_32_24: [blackbox] stopped (44217 drops)
2017_04_10_07_32_38: Already landed, not executing RTL
2017_04_10_07_32_38: RTL: completed, landed
2017_04_10_07_32_45: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_32_49: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_32_55: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_33_37: REJECT OFFBOARD
2017_04_10_07_33_38: REJECT OFFBOARD
2017_04_10_07_33_38: REJECT OFFBOARD
2017_04_10_07_33_39: REJECT OFFBOARD
2017_04_10_07_33_41: REJECT OFFBOARD
2017_04_10_07_33_41: REJECT OFFBOARD
2017_04_10_07_33_42: REJECT OFFBOARD
2017_04_10_07_33_43: REJECT OFFBOARD
2017_04_10_07_33_43: REJECT OFFBOARD
2017_04_10_07_33_43: MANUAL KILL SWITCH OFF
2017_04_10_07_33_44: REJECT OFFBOARD
2017_04_10_07_33_45: REJECT OFFBOARD
2017_04_10_07_33_46: REJECT OFFBOARD
2017_04_10_07_33_46: REJECT OFFBOARD
2017_04_10_07_33_47: REJECT OFFBOARD
2017_04_10_07_33_48: REJECT OFFBOARD
2017_04_10_07_33_49: REJECT OFFBOARD
2017_04_10_07_33_49: REJECT OFFBOARD
2017_04_10_07_33_50: REJECT OFFBOARD
2017_04_10_07_33_51: REJECT OFFBOARD
2017_04_10_07_33_51: REJECT OFFBOARD
2017_04_10_07_33_52: REJECT OFFBOARD
2017_04_10_07_33_53: REJECT OFFBOARD
2017_04_10_07_33_53: REJECT OFFBOARD
2017_04_10_07_33_54: REJECT OFFBOARD
2017_04_10_07_33_54: REJECT OFFBOARD
2017_04_10_07_33_55: REJECT OFFBOARD
2017_04_10_07_33_56: REJECT OFFBOARD
2017_04_10_07_33_57: REJECT OFFBOARD
2017_04_10_07_33_57: REJECT OFFBOARD
2017_04_10_07_33_58: REJECT OFFBOARD
2017_04_10_07_33_59: REJECT OFFBOARD
2017_04_10_07_34_00: REJECT OFFBOARD
2017_04_10_07_34_01: REJECT OFFBOARD
2017_04_10_07_34_01: REJECT OFFBOARD
2017_04_10_07_34_02: REJECT OFFBOARD
2017_04_10_07_34_03: REJECT OFFBOARD
2017_04_10_07_34_04: REJECT OFFBOARD
2017_04_10_07_34_04: REJECT OFFBOARD
2017_04_10_07_34_06: REJECT OFFBOARD
2017_04_10_07_34_07: REJECT OFFBOARD
2017_04_10_07_34_07: REJECT OFFBOARD
2017_04_10_07_34_08: REJECT OFFBOARD
2017_04_10_07_34_09: REJECT OFFBOARD
2017_04_10_07_34_10: REJECT OFFBOARD
2017_04_10_07_34_11: REJECT OFFBOARD
2017_04_10_07_34_12: REJECT OFFBOARD
2017_04_10_07_34_13: REJECT OFFBOARD
2017_04_10_07_34_13: REJECT OFFBOARD
2017_04_10_07_34_14: REJECT OFFBOARD
2017_04_10_07_34_15: REJECT OFFBOARD
2017_04_10_07_34_16: REJECT OFFBOARD
2017_04_10_07_34_16: REJECT OFFBOARD
2017_04_10_07_34_17: REJECT OFFBOARD
2017_04_10_07_34_18: REJECT OFFBOARD
2017_04_10_07_34_19: REJECT OFFBOARD
2017_04_10_07_34_20: REJECT OFFBOARD
2017_04_10_07_34_20: REJECT OFFBOARD
2017_04_10_07_34_22: REJECT OFFBOARD
2017_04_10_07_34_23: REJECT OFFBOARD
2017_04_10_07_34_23: REJECT OFFBOARD
2017_04_10_07_34_25: REJECT OFFBOARD
2017_04_10_07_34_25: REJECT OFFBOARD
2017_04_10_07_34_46: PREFLIGHT ADVICE: ACCEL SENSORS INCONSISTENT - CH
2017_04_10_07_34_46: ARMED by RC
2017_04_10_07_34_47: [blackbox] /fs/microsd/log/2017-04-10
2017_04_10_07_34_47: [blackbox] recording: 07_34_46.px4log
2017_04_10_07_34_47: Takeoff detected
2017_04_10_07_34_57: REJECT OFFBOARD
2017_04_10_07_34_57: RTL: return at 5 m (0 m above home)
2017_04_10_07_34_57: RTL: descend to 5 m (0 m above home)
2017_04_10_07_34_57: RTL: land at home
2017_04_10_07_34_58: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_34_59: RTL: completed, landed
2017_04_10_07_34_59: Landing detected
2017_04_10_07_35_01: DISARMED by auto disarm on land
2017_04_10_07_35_01: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_35_02: [blackbox] stopped (864 drops)
2017_04_10_07_35_02: REJECT OFFBOARD
2017_04_10_07_35_47: MANUAL KILL SWITCH OFF
2017_04_10_07_36_09: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_36_18: Using minimum takeoff altitude: 2.50 m
2017_04_10_07_36_53: MANUAL KILL SWITCH ENGAGED
2017_04_10_07_36_54: Already landed, not executing RTL
2017_04_10_07_36_54: RTL: completed, landed

http://logs.uaventure.com/view/b9xqTXiMhc9YzynSioyAiW

What is RC_MAP_KILL_SW set to?

in QGC kill SW is ch8