Got my first glitch today but I'm not sure what is causing it. While hovering it will suddenly roll to the right. When I correct it with a left input on the stick it seems to go away. It seems to happen every few minutes and is the same reaction each time. I recently shimmed the gears in the tail gear box because of excessive slop. and it now seems to make noise in the gear box, a whine. Could I have shimmed it to much? I am flying a 96 version XCell 60ST, OS 61wc, Futaba 8uhps.