I had a simular problem with mine...3 things to check

1) antenna routing..it does not need to touch the carbon tail boom. Either wrap around a straw or go with a Deans or other base loaded antenna.

2)Tail motor....the stock tail motor is a piece of junk and does not last long..mine made about 6 hovers and then quit

3) Battery charge....are you using a peak charger or the one supplied with heli? Over charging a NiHm make it do funny things


hope something here helps

James