I just had a frustrating afternoon trying to fix exactly the same kind of problem on my Piccolo. I tried everything I could think of. In the end I discovered it was just the negative and positive cables to the tail motor that needed reversing (goodness knows how I got them the wrong way round in the first place - I've been flying the thing for years!)

Although it now seems obvious, it didn't look that way right up to the point where I switched the cables around. I was sure I had a serious problem and at one time had decided that the gyro had packed-in

Hope you find the cause of your problems

Tony