so ive been dealing with this for a few days now and im losing my mind a little. built a 5inch freestyle quad a couple months ago, been flying it pretty regularly with no issues. last week i crashed kinda hard into a tree branch, nothing looked obviously broken, props were fine, frame had a small crack but nothing structural.

now when i arm it, motor 3 just twitches like twice then stops. the other three spin up fine. if i give it full throttle sometimes it kicks in but then cuts out again mid-flight which is obviously terrifying. ive already resoldered the motor leads to the esc because one joint looked a little cold, didnt fix it. motor temps after a short run seem normal on 1 2 and 4.

running blheli_32 on all four escs, 2306 motors. anyone seen this before, is the esc just toast or could it be the motor itself? i dont have a spare motor to swap test right now which is annoying

pull the motor off and spin it by hand, feel for any grinding or rough spots in the bearing. tree hits can bend the shaft just enough that it binds under load but feels ok when you manually spin it slowly. if the shaft is bent even a tiny bit the esc will see the back-EMF going weird and either desync or just cut out to protect itself. blheli_32 is pretty sensitive to that stuff.

also worth connecting to blheli suite and checking if esc3 is throwing any errors or if its settings got corrupted from the impact. ive had settings revert to defaults after a hard crash before which causes all kinds of weird behavior. demag strength in particular can cause exactly what youre describing if its set wrong for your motor kv.

had almost the exact same thing happen to me, turned out to be the motor. looked completely fine visually but one of the stator windings had a partial short from the impact. you can check with a multimeter across each pair of motor leads, resistance should be equal across all three combinations. if one pair reads noticeably different then the windings are damaged. escs are usually pretty tough, motors take the hit first.