Two Dogs,
I had this same problem with my bobcat 460T gyro. If you read the instructions closely on this gyro they say that it will shift center slightly when the gain is increased or decreased. I sent mine back to horizon also and they said it was normal. After being told by several of the guys at my field that it was not normal I sold my 460 and found 3 of the discontinued 450's from various hobby stores.

If you are using the 460T on the bobcat switch it out and see if you can find a G450 (highly unlikely, but maybe). It cured the problem with it switching center.

Patrick.