i'm having that problem too, and i wired and zip tied the whole cage up, except the roof, which i have a towel upon. they haven't escaped yet, but i just cleaned them, and they're so excited all they're doing is escaping!
i got rid of my previous cage, and now I'm worried that i'm going to have rats running around, and I've got 2 dogs and 2 cats.
More zip ties and wire, here I come!