Decreasing z axis in mavros even when disarmed


I am trying to autonomously move my drone using mavros by sending waypoints to mavros/setpoint_position/local. For local position I’m using arkflow sensor and subscribing the topic /mavros/local_position/pose.

Some initial flights are ok. But after a few minutes the z axis in /mavros/local_position/pose increasing gradually or decreasing so much that when the drone is disarmed it would even give -4m in z axis.

If i turn off the drone, and test it a few hours later it will be fixed again.

You can see -4 z axis local position estimate in:

@bresch can you please take a look?