so ive been dealing with this for about a week and its driving me nuts. one of my rear motors on my 5inch freestyle build starts twitching when i throttle up past like 30% and then sometimes just cuts out completely for a split second before catching again. its not consistent which is the weird part, sometimes its totally fine for a whole pack and then other times its doing it every few seconds.

i already swapped the prop on that motor thinking maybe it was a balance issue but that didnt change anything. the motor itself is a T-Motor F40 pro iv and the ESC is a 4in1 hobbywing x4 so not exactly cheap garbage. checked the motor screws, theyre fine. checked the motor bell for any wobble, seems normal. did a motor test in betaflight and i can hear a slight grinding noise during the test but its really faint.

my gut says its the motor but i dont want to spend $35 on a new one if its actually the ESC signal or a bad solder joint somewhere. anyone dealt with this before?

that grinding on motor test is almost always a bad bearing or a stator wire thats starting to come loose internally. ive had the exact same thing with a T-Motor F40 after a pretty hard crash, looked totally fine externally but one of the phase wires inside was partially broken so it was making intermittent contact. the twitching at partial throttle makes sense because thats when the ESC is doing a lot of rapid switching and a flaky connection will show up way more than at full throttle where its basically just on.

honestly just pull the motor and spin the bell by hand real slow, if you feel any roughness or a slight catch in the rotation its the bearing. if it spins smooth but you still get the grinding sound in betaflight motor test then id start looking at the phase wires where they exit the motor can. ive resoldered that joint before and fixed it but its fiddly work and usually not worth it for a motor thats already showing problems.

could also be a desync if youre running rpm filter off or have dshot600 with a longer wire run to that ESC corner. not saying it is but ive chased what i thought was a mechanical problem for ages and it turned out to be desync artifacts on one axis. switching to dshot300 actually fixed it for me on a similar hobbywing setup