Good Sunday morning
I have several Electrics,Electronics & Dynabeats that seem to run fine for awhile but then start and stop or just slow down. I was told that the contacts were dirty and they would have to be taken apart and cleaned and or the contacts replaced. This is above my skill level at this point so I elected to buy some electronic contact cleaner ($10)from Radio Shack and give the mov'ts a good skirt. Has woked for me on most but not on all.
Good luck - I know someone else may have some better suggestions