Vtol forward motor stop

Hi my friends
i am using a cuav V5 plus in a Vtol and in some of my flights when i do mission,the aircraft start to take of and reach to the take of altitude and when it going to transition to wing,the forward motor start to work snd after 1-2 seconds it stop and the aircraft hover with its quad motors.also the video get freezed and i have to change to qloiter mode.this is one of my bin files when this error happened

I would appreciate if you can help me with this issue