Position vs Stabilized mode and throttle

When flying in position mode I have no problems with the throttle at center stick during arming process. Today my drone on the first flight flew in position hold, with my throttle stick in center position I armed the unit then I went from center position to about 75% throttle it flew great.

My second flight the drone would not go into position mode, but in stabilized mode it did not arm because it said that the throttle was not at zero while it was in center stick. Pulled my throttle all the way down . The drone shot up in the air and when I tried to bring it back down it lagged and then came down hard, and crashed. We have and experienced pilot so we can rule that out. lol.

Im thinking that the drone would not go into position mode because I changed the location of the GPS module and did not recalibrate? Also, when using a joystick that sits at center position should we be using throttle zero all the way down? Or throttle zero at center stick?

Our minimum PWM when our motors turn right now is 970. This seems low so could it be an ESC calibration problem or a PID tuning problem?