Is that actually stapled?
What holds the corners together?
This is the bed base correct?
Not really.There was a piece of corner molding stapled to it that fell off.
Another picture.Yes. There was a corner molding that came off.
I see staples in your pic. Do you? the frame looks to be pushed out from the inside. Too much stuff crammed under the bed?
It looks stapled together which isn't strong whatsoever. If it were me, I'd fix it myself with some glue and screws.
I think it's those strut/spring devices pushing it out when the bed comes down.