Copter failed in mission


I have a copter with LightWare Lidar with a maximum altitude of 120 m. The purpose of the mission was to check a copter behavior over water when the LIdar has less altitude range than over a solid ground (specs says it is about 40 m). Mission was set to fly to a WP over water at 60 m, then another WP over ground and RTL from there. During a mission flight, the copter reached the first WP and at this point RTL engaged, probably due to missed terrain (Err. 23-1 in the log). This was anticipated as a possible result when Lidar lost the ground. What was unexpected, that the copter suddenly started to fast climb for some reason, quickly reached enormous 1000 m. When I caught the control over the vehicle it was way too high and RTL engaged itself several times due to low RSSI failsafe at the limit of the radio range. I never obtained the full control so eventually the vehicle crashed by the loss of a power. Fortunately I was able to find it and got a log which I attached to the post. At my view the weird things happened at about 90 sec. when for some reason the EKF switched to EKF2 back and forth (Err. 24-1, 24-0) and first RTL was engaged. That’s when unexpected climb has started. CTUN.DAlt shows steady ‘0’ until 136 sec. for some reason while BAlt shows a fast climb out at this time. Could anybody explain what happened?

I use PX4 under 3.4.3,
LightWare Lidar SF11/C
Log file:!AieROjktQIZ3jVHU-7gMKcLKh_0k

Thank you in advance!