We used the software version of the autopilot Ardu Plane V3.8.0 Beta 3.
The work of the autopilot did not have problems with this software.
But in one of the flights there was an incomprehensible situation with altitude, a flight altitude of 50 m was set, and the aircraft flew at an altitude of more than 100 m, and we observed it visually and this was then shown by telemetry in flash memory, see figure
The same height value was given by the GPS sensor. Thus, our aircraft flew more than 50 meters higher than the flight altitude was set!
And in the subsequent flights, after switching off the power of the autopilot, this problem was no longer observed!