so this has been driving me crazy for like two weeks now. im running a 5inch freestyle build, T-Motor F40 Pro IVs on a Mamba F7 stack and one of my motors started doing this weird thing where it twitches when i arm it, like tries to spin then just kind of gives up. the other three are fine. i've already checked the soldering on the ESC pads and everything looks clean, no cold joints that i can see.

i swapped props thinking maybe a blade was bent or something causing resistance but same behavior. also reflashed BLHeli and recalibrated but still the same deal. the motor itself spins freely by hand, no grinding, no notchiness at all. temps seem normal after flying on three motors (yeah i know, not ideal).

is this an ESC channel issue or could the motor actually be dying even though it feels fine? i dont really want to drop another 30 bucks on a motor if its actually the ESC that's shot

plug the motor into a different ESC channel and test it, thats the fastest way to narrow it down. if it twitches on a new channel the motors toast, if it runs fine then yeah your ESC channel is done. ive had BLHeli32 ESCs where one channel just gives out while the others keep working, its annoying but not uncommon especially on cheaper 4in1 stacks that run hot a lot.

also check in BLHeli configurator that the individual channel is actually communicating properly, sometimes a channel will show weird or not respond to input changes and thats usually a sign the FET on that channel is partially fried. could also try lowering motor timing on that channel and see if behavior changes at all, but honestly the swap test will tell you everything you need to know in like 2 minutes.

had almost the exact same thing on my build last year, turned out to be a tiny strand of solder that had bridged two pads internally on the 4in1, couldn't see it at first glance but when i hit it with more light and a magnifier it was right there. might be worth another look before you start swapping hardware