It shouldn't be doing that something is wrong. Is the top hinged at the back and make sure you have your poles the right way up - the hoops attached to the sticking out screw under the top bunk and the bottoms in the metal holders?
I don't travel with my bunks set up though.
We may need pics if all of above sound right.
I know they don't have a really high weight
limit (under a 100 lbs?) but they are good for small children . I use mine for storing bags etc and they never fall