so this has been driving me nuts for about two weeks now. one of my rear motors on my 5inch freestyle build starts twitching when i throttle up past maybe 40% and it's not consistent, like sometimes it's fine for a whole pack and then other times it does it on the very first punch. i've already resoldered the motor leads thinking maybe a cold joint was the issue but it still does it.

running 35amp escs (the cheap blheli_s ones, i know i know) and 2306 2450kv motors. betaflight shows the motor output looks clean in the motor tab, no obvious spikes. i swapped the motor to a different esc slot and the twitch followed the motor so i'm like 90% sure its the motor but wanted to sanity check before i bin it. maybe a bent shaft or something internal? it doesn't vibrate any more than the others on the bench.

anyone had this exact thing where it's definitely the motor but no obvious physical damage?

yeah the twitch following the motor to a different esc slot is basically the answer right there, ive had this exact thing twice and both times it was a partially shorted winding inside the motor. you can sometimes confirm it by spinning the motor by hand slowly and feeling for a rough spot or a dead zone in the rotation. if it feels notchy in any way compared to your other motors just bin it, rewinding a 2306 isnt worth the time unless youre really into that sort of thing.

also worth checking the bell for any tiny cracks near the magnet seats but honestly if the twitch follows it, its toast.

could be a bad bearing too not just the windings. i had one that sounded totally fine but the inner race was slightly loose and it would cause weird behavior under load. spin test wont always catch it.