A few years ago, after my original galvanized nesting boxes rusted away, I bought a bank of 4 Kuhn plastic nesting boxes that are have plastic inserts in the bottom. While they clean easily every once in a while they fall through. This makes my birds mad as heck--especially if they are in a lower nest--and results in a few broken eggs. Anyone else have this problem and/or a solution? I'm always careful to make sure they're wedged in but gravity takes over every once and a while and down one goes.