I had the same issue but found it early on. I cleaned the camper real good and put the cover on for the first time. Lucky I was checking it one day and when I pulled back the night shade over the bed vent I found a mouse nest on top of the screen under the vent hood. I unzipped the cover and found a lot of mouse dropping on the roof. I cleaned it all up and two days later it was all back. I still don't know how they got under the vent cover. The cover gave them a way to climb up to the roof. They did chew a couple of the straps off the cover to help in the nest building. I removed the cover and solved the problem. I will never use the cover again.
3 or 4 years back we had some critter climb out TT cover,,, and it eat very large holes in the cover ??? Have no Idea what it was,,, coon maybe ???
We have never seen a Squeal in our yard !!! Only have Pine Trees !!!