Bad brushes in the motor? (no, not the cleaning brushes) How old is it? The overload is a manual reset is it not. Not automatic. How about the outlet the unit is plugged into. Plug a light into it and watch to see if the light remains on if the vac goes out. Outlets in RV's bite into the wire and are a POS. Vampire outlets cause a LOT of trouble in RVs and usually affect only that outlet, not others downstream. A plugged hose allows the motor to run without working so the current goes down so the overload should not trip or reset.