When we got our 2009 27' FB it had the original trailer queen mattress. When showing a friend all of the storage under the bed, I lifted the end of the bed and when I tried to lower it, I had the same problem you did, it just would not close. I thought I was using reasonable pressure to close it but thought it was stuck open and thought there might be some kind of "trick" to get it closed (and really didn't want to break our new AS). After calling the PO, he assured me if I really leaned on it, I wouldn't break anything. He was correct! A couple of days later we replaced the original mattress with a FULL sized queen mattress and with its extra weight we never had that problem again. As an added bonus, we have a much more comfortable nights sleep.
Scott, Becky & Heidi (our standard poodle and travel companion)
Remember... No matter where you go, there you are...
2009 27FB International Ocean Breeze
2010 Toyota Tundra CrewMax, 5.7L V8, 4x4