I'm afraid to ask...

I am fortunate enough to have received a '99 3023 from my mother as a gift last summer.  We stored it for the winter, and when we popped it up a few weeks back, there was white shaving "stuff" all over the place.  Actually, not all over, just in the top/outside fold down portion.  When opened, though, it found it's way onto the couch, bed, and curtains quickly.  I vacuumed and vacuumed, there was lots of this "stuff" in the cabinets at the front/top of the trailer.  The "stuff" was mostly white, but had some brown as I got up front towards the cabinets. My fear is that there is something between the walls that is chewing them up and making sawdust out of my trailer ... could be?  I had it all cleaned, took lots of time to vacuum, then I went out this morning to see a new pile on top of a curtain. Above the curtain, where the "Hot Wheel" looking tracks are, there is a break, a spot where they are to be joined, and that is where the "stuff" looks like it is coming from.
Help ... any advice would be appreciated!
Amy