I would have a go at taking each wire off it’s commutator tag and removing as much solder as possible from it. Then wrap the wire back around it and get some needle nose pliers and just squeeze it tight, then run some new solder back on again. I have just done this to a similar problem on a Flyer PA diesel armature and it ran fine again.
While you are at it make sure you clean any old oil/carbon gunge from the commutator slots as this will cause problems as well.
Do you have any pictures so we can have a look at it?
You have nothing to lose if it went faulty.
