so ive been chasing this problem for like three weeks now and im losing my mind. quad took a pretty hard hit on motor 3 a while back, bent the shaft obviously so i replaced the motor. new motor goes in, spins fine in betaflight motors tab, but in actual flight it stutters and the quad wants to pull hard left on any throttle above like 40%.

heres the thing ? i already replaced the ESC on that arm thinking it was toast. still doing it. checked the solder joints twice, reflowed them, nothing. pid tuning doesnt fix it, i tried throwing iterm relax at it and adjusting filtering but it still twitches. the motor itself tests fine when i spin it manually, no grinding, bearing feels smooth.

only thing i havent done is replace the flight controller. starting to wonder if its a damaged motor output pad or something on the FC itself causing weird signal. has anyone seen this where the issue is actually upstream from the ESC? feels weird because the other three motors are totally normal.

yeah this sounds like it could be a damaged signal trace or pad on the FC honestly. ive had a similar thing happen on an older F4 board where one motor output just got flaky after a crash ? everything downstream tested fine but the signal coming off that pad was garbage. you can actually check it with an oscilloscope if you have access to one, compare the signal waveform on motor 3 output vs a known good one. if you see noise or the pulsewidth is drifting thats your answer.

also worth checking if your ESC is running DSHOT or analog PWM ? if its DSHOT try dropping to a lower DSHOT value like 300 instead of 600 just to rule out signal integrity issues on that line. its a bit of a hack but it helped me narrow down a problem once.

did you check the prop on that motor too? i know it sounds dumb but a slightly cracked prop arm or even a tiny imbalance on one blade will absolutely cause stuttering that looks like an ESC or motor issue. betaflight tries to compensate and it just makes it worse. ive been fooled by this more than once