I use the same method CW uses to fix all of those motor types. There is supposed to be a ball bearing in the bottom of the plastic plate that holds the armature shaft. The problem is often the plastic bearing plate is too far to one side. If you look inside the C shaped opening where the armature spins you can usually see which side the armature has been rubbing causing it to climb upward. You then move the bottom plastic plate to the opposite side and hold it in place with a wedge of plastic or card stock. I usually put a dab of CA glue there once I have it correct.
Rob
