Michael, if its glithing that way with the engine off then its time for some drastic testing. Go down to one receiver and plug in one servo and test, add another servo and test, add another servo and test, etc. Keep testing til the problem shows up. If the first servo causes a glitch swap it with another and see if the problem goes away. Change receivers and do it all again. At some point you will narrow the problem to one component.

BTW, if its truly tail heavy when you balance it correct this situation before you fly it the first time......

Ed M.