@george-kollamkulam : the problem with the drone shooting straight up in position mode seems related to bad estimation of altitude. In particular, if you are flying indoors (no GPS signal accessible) GPS needs to be eliminated from the altitude estimation since the lack of GPS signal in the sensor fusion seems to cause the problem.
IN summary, if you are flying indoors and experience this problem, try disabling GPS in PX4 by setting the parameter SYS_HAS_GPS to "disable" in QGroundControl. That seems to have resolved the issue for us - at least for now.