Before you do anything to the motor, try recyling the disconnects -- both house and chassis to off, wait about 45 seconds, and then turn them back on. This resets the Vansco system breakers, if you have them. When our step does this, usually because I started the engine and closed the door with the shore power hooked up, it screws up the system. I disconnect shore power, shut down the engine, recycle the disconnects, and move on, and it has always worked to restore the step. Maybe it will work for you.
TerryM has a work-around to this that he's going to show me at our next rally, but this process always works for me.
If it doesn't work for you, then it may be the motor or otherwise, but this is a "cheap" start to checking the problem.
Former Owner, 2006 36MDDS
2010 Arctic Fox 22GK Travel Trailer
2007 Toyota Tundra