Bathtub Caulk Repair Tape
You might try looking in the plumbing section of your local hardware store for some bathtub repair tape. It is a smooth, silppery, white plastic tape, about 1 inch wide, with adhesive on one side, and is made to repair, or at least cover up, the caulk joint between the bathtub and the wall. Just slide your hatch completely open, peel the paper backing from the adhesive, and lay the tape in the groove where the hatch slides. The adhesive keeps it in place just fine. In my case, it made the hatch slide much more easily, and may eliminate your squeek.