Tetrix motor not working

[groudonkoorb]

Our team has a motor that had some wire soldered on the terminals. There was so much wire and solder that we could not get the power wire for the motor on. we used a soldering iron to heat up that solder and pulled out the wires with pliers. we then tested the robot and the motor ran fine, but a while later when we tested it again that one motor did not move. we tested that motor power wire on a different motor and that ran, so it is not a problem with the code or wire. The power terminals on the motor have a little bit of solder on them, but not much and it worked for a while. Has anyone had a similar problem, or know a solution? Thanks