ok so ive been dealing with this for like 3 weeks now and im losing my mind. running a 5inch freestyle build, F7 stack, Aikon AK32 35x35 4in1, motors are T-Motor F40 2306 1750kv. every few packs i get this violent twitch on one arm ? always the same arm ? and it either tumbles or i catch it low and land fast. happened twice over concrete already and somehow havent broken a motor yet.

things ive tried: reflashed ESC firmware (tried both BLHeli32 and switched over to AM32 to see if that helped), rechecked all motor screws, resoldered the motor leads on that corner because one joint looked a little cold, checked for prop strikes on the shaft, ran motor tests in betaflight and everything spins smooth. changed the prop on that arm too. desync errors are showing up in the blackbox on that motor, rpm goes nuts for like 200ms then recovers or doesnt.

not sure if its a motor bearing starting to go or if theres something weird happening with that specific ESC leg. temps seem normal. anyone dealt with this specifically on a 4in1 where its just one corner acting up?

had almost the exact same thing on a Mamba stack last year. blackbox showed the same rpm spike pattern. ended up being the motor ? bearing was fine but one of the windings had a partial short that only showed up under load. ohm'd out fine on a multimeter but when you spin it up and it heats a bit the resistance changes. swapped the motor and never had it again. if you havent already just throw a known good motor on that arm and fly a few packs, its the fastest way to rule it out before you go digging into the ESC.

also worth checking your motor screw length on that arm ? sounds dumb but ive seen longer screws bottom out and make intermittent contact with the windings through the motor bell, especially after a few crashes shift things around. probably not your issue but its a 30 second check. also what RPM filter settings are you running in AM32, some of the defaults are pretty aggressive and can cause weird feedback loops on a 4in1 if one pad has slightly higher resistance than the others from a solder joint.