so ive been chasing this for like three weeks and im starting to lose my mind a little. running a 5inch freestyle build, f7 stack with the hobbywing xrotor 45a escs, 2306 2450kv motors. everything is fine at mid to full throttle but around 10-20% stick input one of the rear motors just... twitches. not a full desync, doesnt flip the quad, just this stuttery hesitation that i can feel through the sticks and see in the blackbox traces.

ive tried bumping the timing up, swapping motor order in betaflight, even reflashed the esc firmware. the weird thing is it only does it on that one motor but ive already swapped the motor itself to a spare and the problem followed the esc position not the motor. so its definitely that esc but the esc reads fine in blheli, all the settings look identical to the other three.

someone suggested it might be a cold solder joint on the phase wires but i reflowed all three and it still does it. at this point im wondering if maybe the esc itself has a bad fet or something internal. anyone dealt with this before or should i just replace the whole stack and call it a day

had almost the exact same thing on a tmotor f45a a while back. turned out to be one of the phase wires had a hairline crack inside the silicone insulation, looked totally fine on the outside but there was a partial break in the conductor. you could only see it when you flexed the wire a certain way. wouldnt have found it without cutting the insulation back.

before you replace the whole stack id try swapping out the phase wires entirely on that esc, like actually desolder and replace them rather than just reflowing the joints. if the problem is mid-wire theres nothing reflowing the ends will do. worth 20 minutes before you spend money on a new stack.

might be a dumb question but did you check the motor screw on that corner? i had twitching that drove me crazy and it ended up being one screw slightly loose letting the motor wobble just a tiny bit under load. blackbox looked weird on it too. probably not your issue if it followed the esc position but just throwing it out there