Plane in failsafe RTL is descending to ground even it shouldn't

Due to ELRS TX module problems I had yesterday several “real” RC failsafes and was very lucky that my plane actually didn’t crash.

After a FS event it performed propely FS_SHORT and FS_LONG actions where FS_LONG_ACTN was RTL. It really begun returning, but instead of returning 100m above the terrain as I (hopefully) set, it performed “perfectly controlled descending” until I (fortunately) regained the control by changing the flight mode 40 meters above the ground.


Here is the capture from the log.
Green is altitude required by the autopilot, red altitude above home and orange altitude above the terrain. Light blue stripe on the top shows duration of the RTL mode

It’s visible, that green (required altitude) stops at about 100m while red and orange (real alt) keep lowering much lower than this.
Of course the plane was armed, had enopugh power and battery etc…

It’s obvious, that the descending was done by FC “by purpose”, but why? RTL_AUTOLAND=0.
The same thing happened 3 times the same way.
Does anyone have any explanation what can be wrong?

The only “abnormal” thing in my setup was, that plane wasn’t controlled by standard RC protocol (like CRSF), but using the new ELRS “MAVLINK” feature by RC overrides.Plane is X-UAV mini Talon, FC Omnibus F405.
Here can be downloaded the logfile.
Thank you for any hint!