RE: Motor Twitches Forward and reverse
Good solder joints have a shiny appearance. The damage may be in side the motor. One of the winding leads may be loose; a magnet could be also. You can check the continuity of the esc to motor leads with a VOM. Magnets can be epoxied back (be sure of the orientation).
Finding something like this takes time and patience - or else you throw money at it and buy new equipment (-:
Walt