this has been happening for a few weeks now and its driving me insane. basically im flying, everything feels fine, and then suddenly the quad just drops out of the sky like one corner gave up. managed to catch it low a couple times but i've binned it twice because of this. its the same motor every single time, rear right.

ive already swapped the motor twice thinking it was just a bad motor but same thing keeps happening. props are balanced, the arm looks fine. the weird thing is when i plug back in on the ground after one of these incidents the motor spins up completely normal, all four sound the same, no issues. its like it never happened.

running a 4in1 ESC so i cant just swap that corner easily. running 4s and its not a voltage sag thing i dont think because it happens at different points in the flight, not just when im hammering it. anyone dealt with something like this

sounds thermal to me. if its a 4in1 and one corner keeps doing it, could be that specific ESC channel is running hotter than the others ? maybe airflow blockage in the stack, or a fet thats already been partially cooked from a previous crash or overcurrent event. the fact that it works fine when its cooled down on the ground is a pretty classic sign of thermal shutdown or a component thats marginal when hot.

worth pulling the stack and actually looking at the ESC board closely, especially around that rear right section. sometimes you can see a slightly discolored fet or a cap thats bulging a tiny bit. also check what temperature your ESC is logging if you have blackbox enabled, though i know not everyone logs ESC temp.

had something weirdly similar and it turned out to be a motor bullet connector that was only making partial contact. looked totally fine, motor spun on the bench no problem, but under vibration and load one of the phase wires would momentarily lose contact and the ESC would just cut. resoldered all my connections and never had it again. probably not the same thing but worth ruling out if the thermal angle doesnt pan out