this shown Motor Angel should not be the rootcause for the fligtbehavior, you described.
Have you looked at the Wing for any mismatches or distortions?
What About the Trim at the Rudder? Isit trimmed to the left direction.?
And what I have at my Funman, weres the Vibrations of the whole Model as I speed up my throthle.
This high Vibrations were cause a trange controlbehavior of the Model.
I prepared the engine in the engineholder stronger and go to the newtral Angel of the Engine an Propeller direction.
Please Control this Questionmarks.