This caused me a bit of challenge. It happened after a very slight bump broke a blade. I balanced a new set and put them on. I couldn't get the run out right and there was overloading of the motor causing the ESC to bail out and shut down. I tried the loose and tight blade grip stuff but it didnt seem to be the sweet spot solution, a different set of blades and no change. So back to the workshop, I stripped the head and there was no binding or anything obvious. When I pulled the feathering shaft out it looked OK until I held it up to the light against the straight edge of my vernier. There was an ever so slight bend in it. So in with a new feathering shaft and it seems to have solved the problem.
