this has been driving me nuts for like two weeks. rebuilt a quad after a pretty minor crash, nothing looked damaged, but motor 3 keeps desync'ing mid-flight and dropping out for a second before coming back. sometimes it doesnt happen at all on a short pack, other times it does it three times in a row and nearly puts me in the ground.

ive already resoldered the motor leads to the ESC because i thought maybe a cold joint was the issue ? looked fine visually but redid it anyway. same problem. swapped the motor to a known good one from another quad, same behavior on that ESC. so at this point im pretty sure its the ESC itself on that corner but i wanted to ask here before i just rip the whole stack out.

its a 4in1 so thats kind of a pain. running BLHeli_32, have tried adjusting timing and demag settings in the configurator but honestly im not sure i fully understand what those settings actually do at a practical level. any ideas what else to check before i just order a replacement

demag compensation is worth actually digging into if you havent ? high demag can cause issues with certain motors especially if theyre high kv or have a lot of poles. but if you already swapped to a known good motor and the problem followed the ESC, that pretty much tells you what you need to know. the ESC is cooked or at least that phase is marginal.

one thing i'd check before pulling the stack ? look at the motor output pads under magnification if you have it. sometimes there's a hairline crack in the trace or a lifted pad that you can only see if you're really looking. also worth checking your ESC telemetry logs if you have blackbox, temperature spikes or current anomalies on that channel would confirm it pretty fast. but yeah if it's a 4in1 and one channel is bad, you're kind of just replacing the whole thing unfortunately.

what ESC is it? some of the cheaper 4in1s have a known issue with heat on specific FETs under load and it gets worse after a crash even if nothing looks wrong. i had a Mamba that did basically exactly what you're describing and turned out one of the FETs was just on the edge of failing. ran okay cool but as soon as it got warm it would act up. ended up being a $40 lesson in just buying a replacement instead of chasing it for a month