Hi Smoke Stack Lightnin,
I have read your problems with your Royal Blue. I think you have an armature which is hitting the brush tubes. In the motor there are some spacers to relieve the slack or the armature from front to rear when it changes directions. There might be spaced too close to the bottom of the brush tubes which causes the armature to hit them on the armature face and scar it.
Remove the brush plate and armature and check the spacers and adjust accordingly so that the armature is slightly away from those tubes. The engine should run very quietly after the adjustment and spaced loosely between the front bearing and the rear bearing but away from the brush tubes.
Try this and see if that will work. In the mean time I will try to diagnose your other problems.