step issue

First clean the grounding wire connection at the coach frame. There are no limit switches or such to tell the control when the steps are fully retracted or extended. Instead the controller monitors motor current. When the steps hit a limit or obstruction motor current spikes and the controller shuts off power. Poor grounding and you'll get an early current spike. Retraction has a slightly higher current demand due to gravity then extending which could explain why you get full extension.

I'm also thinking may be the drive gear has broken teeth. The gear is cast pot metal and is the weak link in the mechanical chain. Loose a tooth or two and the stairs will stop at that gear position.

Be very careful working on the steps. Unexpected extension or retraction with you fingers in the wrong spot isn't something I even want to think about.