Yep, I have one in the exact same spot on my 8280. I think it is related to the floor not being properly supported around the floor vent. I discovered mine about a year ago. It hasn't gotten any worse so I'm going with the attitude of the fix may cause more problems than the problem. I've placed some padded matts over it to distribute my weight when I'm around it. So far, so good.
2014 Ford F250 Lariat
2014 Rockwood Signature Ultra Lite 8280 WS
Louisiana before, fulltiming since April 11, 2014