I have always read that you do not want to seal the bed ends of a pop up. You want those untreated and open to breathe.
With that said, you shouldn't be grinding away at your beds to the point of creating sawdust. There shouldn't be any drag of the bed. It should slide in and out freely and unencumbered. Somethings sounds wrong to me.
You said it's new, so I recommend calling the dealer.
Every time you use an apostrophe to make a word plural, a puppy dies.
TV: 2019 F-350 Lariat 4WD CCSB 6.7 PSD 3.55, 3,591 lb payload
Former RV: 2018 Rockwood Mini Lite 2504S
Former RV: 2007 Fleetwood/Coleman Utah
Former TV: 2005 F-150 King Ranch 4WD SCrew 5.4L Tow Package