This was mentioned to me by another member here the other day. They had a BP get behind the foam background. Is the hole he is using along the top or the foam or one of the sides? I added additional foam background to the sides in my Exo Terra for the time being, which makes in nearly impossible for anything to get through that way, it creates such a tight corner. For the top or bottom, the only thing I can think to do is put a little substrate down before putting the foam in, helping to seal up any little gaps along the bottom and push the foam upwards slightly, hopefully closing gaps at the top as well.

BTW, that is a gorgeous snake you've got there. I don't know anything about scrubs, but now I am curious...