On one of my first flights with the Phantom i realised i was a bit too optimistic about my flying skills. The Phantom crashed into the sand and when i tried to start up the Phantom again, one of the motors is not spinning anymore. Instead it sort of twitches back and forth a bit a few degrees. I haven't tried switching motors yet, because i also have some problems opening the case. However i noticed that when i take the cap off the motor and do the motor test on the Naza M software the ESC makes a slightly different beeping sound than when i do the same thing on a different motor. I couldn't find any sand or something inside the motor that might be the cause of the problem. How can i be sure this is either a motor or an ESC problem or is there still a way to fix this without buying new parts?