it may not be the case, but i was having issues with one of my 401's on a 450 with an align 520 servo. i switched out my align servo with a futaba servo that i had and it went right back to normal rock solid. i originally had it paired with a 9257 and it was great. moved it to a diff heli with that align 520, and all hell went loose, dunno why, never figured it out, but when i put the 9257 back with it. it was perfectly fine again.