Yesterday I took off props to run some batteries down after about 10 minutes of running one motor made a chirping sound it did this about two or three times during the 40 minutes of running the battery down. Ran second battery down it did the same thing it would appear to start and restart I would estimate like a 10th of a second. Anyone else with experience like this and what could be the problem. Should I replace motor and can I replace motor with stock motor so matches with the other three. On the third battery it did it just one time.