I'm so sorry. That's disappointing. One of my roller pairs always breaks their eggs. I let them try for the last time, and it ended in one broken egg, and the other one cold. They are now going to be flyers. The guy I got them from said that they were extraordinary birds, and to never fly them. Well, it's pointless to keep a non breeding bird from flying, so they are going to fly.
For your birds, I suspect they get off to get an intruder out of the box,and when they do, they break an egg. Can you put cardboard on the front like this?
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I Think it would greatly help.