First off I would like to say I can't beleive the moderator hasn't tried to help you with this question. Secondly
I think you may have posted this question in the wrong area, ARF post room may be where you want to be.

OK , I dont know anything about US Aircore planes, but I have had this problem before with an electric plane. Check to see if the servo tray is moving around. If it is moving even just a little bit then this will be the answer to your problem.

If it isn't moving then make sure the elevator is not moving , then check the servo to see if it is stripped.

Good luck.