UH-OH!! Swing motor problems

[modelman]

Here I am removing the swing motors from my 182M Marion shovel model.

About a year ago I stored my shovel on the shelf to make more room in my shop to work on the mining truck and the shovel was working great. I got it down last week and hooked it up anxious to load my truck with it. The swing motors were causing the radio to glitch so bad I could not operate the shovel. I called a friend of mine who is a genius with this stuff and he said that after sitting for a long time the motors will develope a green bettina on the comm.(similar to what gets on copper), and this will cause the brushes to arc and cause the radio noise. He said I would have to run the motors and let the brushes re-seat to the comm.. I also had never put the noise-suppresion caps. on the swing motors and he said I should do that to. The hoist and crowd motors are working great so I am a little confused why this happened. Has anyone ever heard of this or ever had this problem. I am doing just what he said to do and should know in a few days if this corrects the problem.