so ive been chasing this issue for like three weeks now and im losing my mind a little. running a 5inch quad, betaflight 4.4, blheli32 ESCs. one of my rear motors keeps desyncing mid-throttle punch, not on every flight but like once every 2 or 3 packs. it twitches, drops for half a second, then comes back. sometimes it flips me if im already doing something aggressive.

ive already reflow soldered the motor pads, swapped the motor itself (same thing happened with the replacement), updated blheli firmware, tried demag strength settings, tried different timing. nothing seems to stick. the other three motors are completely fine on the same ESC board so its not the ESC dying i think. could it be a bad signal wire somewhere? or a grounding issue? i honestly dont even know where to look at this point.

had almost the exact same thing last year, drove me absolutely crazy. turned out to be a tiny nick in the signal wire going to that ESC pad, like barely visible, but enough to cause intermittent dropout under vibration. worth checking the wire under some magnification because mine looked totally fine at first glance. also check if the motor screws are maybe slightly too long and catching the windings ? i know thats kind of a longshot but ive seen it cause weird behavior that mimics desync.

if youre on a stacked ESC and its only one corner, could also be worth looking at the via connections between layers if your board uses them. not common but not unheard of either.

what RPM filter settings are you running? i had something similar and it turned out my dynamic notch was not catching a resonance frequency on that arm because one of my prop nuts was slightly loose, so the vibration signature was different from the other arms. blackbox log would probably show it if you havent looked yet, the gyro traces on that axis will look messier than the others right before the desync event