I had that happen to mine. Turned out the main gear had loosened a bit due to the roads and as a result the last tooth on the main gear was destroyed. I ended up getting it repaired with a weld build and grind to make a new gear tooth. Not sure you have the same problem, but with the stairs out if you look at the main gear it will be the teeth farthest from the motor. Since yours is a newer model you can get a replacement gear should that be the issue.
2005 Newmar Kountry Star 3742 - Gas
ACME Eze Tow Dolly
2008 Chevy Malibu Toad