We use the same cot in a lot of our camps; while I have no idea if the fabric has shrunk, I've always had a heck of a time getting that second crossbar in place. That's held true for different cots, different climates, and different years (thus introducing the passage of time).

I usually run out of patience before I get results and end up walking away for awhile (up to and including a couple days). To date the solution has always been:

Just force that mother! Best of luck.

EDIT: Oh, and also what Barbakane said.