Must be one of those Amish tramps? Not a Hobie part there. May be a rope diameter issue.

You can probably help prevent the issue when lacing if this is a three piece.

If you start by tensioning the aft only... the tramp slides aft in the side bars and then reaches the openings. Then, when you tension the center, it pulls out.

Better technique:

Pull the tramp halves all the way forward in the side bars. Use a couple of the center lace grommets and pull tension to seat the side ropes into the side bars (tie off).

Tension the aft laces moderately. Tension the entire length down the center, then finish with full tension on the aft lacing.