Flight altitude of 50 m

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!

Hi, I got similar problem.

AP 3.8 B5

AC set to climb to 50m and then to 80m for all next waypoints. But as the starting sequence finished, it climbed to over 100m with full throttle. Airspeed was too high also. Everything else was perfectly fine on the flight.
(Throttle zero = 1500us)

See here: