LT28 Drive motor problems

[Qweaver]

In "Oh No She won't go" I talked about drive motor problems.  I ordered a used one from WM and it worked for one day and then I had to peck it to finish up the job.  It's working now (still needs an occasional peck) but this worries me. I will put a new brush kit on the old motor and then check out the used one, but I can't put up with this.  No problems for the two years prior to this...but now on two motors.  Any body else having the same recurring problem?