So appareantly there are too many used 5th wheels

We have also experienced this. Had a 08 Excel, excellent shape, that one dealer wouldn't take on trade. They explained exactly as someone suggested here-it was a floor plan problem. As the Excel was a high end unit, they would tie up too much money in the process. They even offered up that if it was a weekend/vacation brand fiver, which they could unload quickly to the oil workers, it would not be a problem for them.

We just moved on to another dealer, but did appreciate their honesty.