winter check up and now a new issue

[LBD]

I went out last weekend to check out how the new to me 19H had wintered. The cover has a few small wear holes but it isn't that bad. There was no evidence of mice moving in but the interior had quite a few dead flies. The most shocking change was the vinyl flooring! It has developed a large bubble that goes from between the sofa and table, to the rear almost in front of the bathroom door. It was not there last fall and I am hoping that maybe it was due to the temperature change. The floor underneath felt solid and I can't think why it would have done this. Hoping now that it is not something I have to fix before taking it out this spring.