so this has been driving me insane for about two weeks now. my back left motor on my 5inch freestyle build keeps stuttering on throttle up, not every time but enough that ive binned it twice already. first thought it was a bad motor so swapped it out with a spare T-Motor F40 i had sitting around, same exact stutter. then i reflashed the ESC with the latest BLHeli32 firmware, recalibrated everything, checked the motor direction in betaflight, ran motor tests and it spins smooth as butter on the bench every single time.

but the moment i put props on and actually fly it, maybe 30 seconds in and it'll just hiccup. not a full desync but close. pulled the blackbox logs and i can see the motor output spiking weird on M4 specifically but i genuinely cannot figure out if its a signal issue or power issue or what. solder joints look fine, no cold joints i can see. ESC is a 4in1 Mamba F55 if that matters.

anyone dealt with this kind of thing before because im running out of ideas here

had almost the exact same thing happen on a 4in1 last summer. turned out to be a hairline crack in the ESC PCB right at the corner pad for that motor output. totally invisible unless you hit it with a magnifying glass and good lighting at an angle. the bench test always looked fine because the board wasnt flexing, but once it was in the frame and getting vibration and flex from flight it would intermittently break the connection. pulled the ESC out of the stack and flexed the board gently by hand and i could actually reproduce the stutter. ended up just replacing the ESC, wasnt worth trying to reflow that area.

worth checking your motor phase wires too though, if one has a nick in the insulation touching the frame it can cause weird stuff under load that doesnt show up any other way.

dumb question but did you check desync settings in BLHeli? like the demag compensation and timing? sometimes bumping demag up a level or two fixes stuttery behavior on certain motor/ESC combos, especially under load. also what cell count are you running, 4s or 6s? some of those Mamba ESCs run a bit hot on 6s and thermal throttling can look a lot like what your describing