Blistering in the poor mans fiberglass a year after build?

I built this camper last February, and it has had a nice smooth exterior since I finished it. I walked past it this afternoon and suddenly it has random bumps on the outside.
It's 2 inch foamboard with canvas glued on and then several coats of exterior paint.
Has anyone else had this problem? Is there an easy fix? Like just popping them and injecting some glue?
[i

It's 2 inch foamboard with canvas glued on and then several coats of exterior paint.
Has anyone else had this problem? Is there an easy fix? Like just popping them and injecting some glue?
[i

