Originally posted by Chopper
You are jumping a tooth on your crown gear. (The white gear on top of the main gear.) This mesh needs to be tight with no slop. You will start taking out teeth on the crown gear if you keep doing this. Make your adjustments to the gear mesh so that the tail take off pinion gear is tight (no pressure but no slop) on the crown gear.
that seems to be the problem, checked that gear and it is unevenly worn, most likely that happened after some ground contact or just aggressive maneuvers...
mesh in tail-box is just very slightly on the loose side, washer would make it pretty tight...
so i won't change the tail, just changed the crown gear and will test fly, i strongly assume this will solve the problem...
thanks everybody