Bud,
What you are describing is most frequently an issue with the small magnetic switch on the frame which is triggered by the magnet on the screen door. The stairs are wired such that they will operate with the engine running so you can exit the coach safely. When the switch is failing, the magnet is out of position, etc. the steps will work erratically.
The second most common problem is dirt in the pivot points on the stairs. When dirty they create enough resistance to stop the motor from moving the steps. I spray mine with WD40 to clean and then with a bit of ATF to lubricate. I find the ATF does not attract as much dirt as silicone or white grease.
