so ive been chasing this for like two weeks now and im losing my mind a little. running a 5inch freestyle build, emax eco 2306 motors, standard 4in1 ESC stack. motor 3 just stutters randomly, sometimes on throttle up, sometimes just hovering. not consistent at all which makes it worse to diagnose.

i already swapped the ESC board with a spare i had lying around, same behavior. so i swapped the motor itself with the one from motor 2 position and the stutter followed the motor not the ESC pad. okay cool, bad motor right? ordered a replacement, installed it, and it STILL stutters on that arm. like what are the odds.

only other thing i can think of is maybe a bad solder joint on the motor wires going into that corner of the stack, or possibly something weird with the signal wire routing. flight controller is a matek f405. betaflight shows normal motor output when i test through the motors tab so im genuinely stumped here.

anyone dealt with something like this where it just refuses to be a simple fix

had almost identical thing on a 4in1 build once. turned out to be a hairline crack in one of the phase wires right where it exits the motor can, you couldn't see it unless you flexed the wire a bit. the insulation was intact so it looked fine but internally it was basically intermittent contact. worth checking all three phase wires on that motor really carefully, like physically bend them slowly while monitoring.

also check if your ESC telemetry is showing anything weird for that motor, desync events or overcurrent spikes. if your FC is logging you might catch something in the blackbox data too, look at the motor output trace and see if there are any weird drops that dont match your stick input.

this might be dumb but did you recalibrate the ESCs after swapping? i had a stutter issue once and it was just that one ESC had slightly different throttle endpoints stored from before and it was borderline desyncing at certain RPMs. also are your motor screws all the way in, a loose motor can cause weird vibration that reads like a stutter but isnt really an electrical thing