During ACRO mode when flying inverted, the plane loses GPS lock, and the plane becomes very unstable, apparently because the speed scaling function fails to recognize that the airspeed calculation is bad. This appears to cause the PID values to be scaled as if the plane was moving at a slow speed. Stall warning is displayed, but the plane is flying normally at high speed.
There needs to be a setting that either ignores speed scaling of the PIDs, or better detection of a lost GPS signal when no airspeed sensor is installed. There’s a calculation that appears to allow limiting the range of PID scaling, however it would be nice if there was a user-defined min and max value for the PID scaling algorithm.