The bolt rope thing is a bit of an enigma...it's worked for a very long time in a lot of different manufacturers but Nacra started struggling with new trampolines staying put right before they went to their side lacing system at around that time your boat was manufactured. I bought a replacement trampoline for one of my I20s then and it immediately started coming out of the track.
The diameter and type of bolt rope used in the trampoline is very important to work with the slot and not damage the slot. There is a chance that the slot in the hull will be cracked once the trampoline starts pulling out (even if it's because the bolt rope was of the wrong size/type).
I think Bach was talking about me - I'm working on making a couple of new side lacing strips for a couple XJ A-cats and the bolt rope was very difficult to find and it was tiny! It's a 3/16" bolt rope that is VERY tightly wound and stiff. After a lot of effort (and help from Bach) I was able to source that bolt rope. Given the trouble I've seen when the wrong stuff is used, I'm not deviating from what has worked on this boat for 8 years already!
If you feel like the bolt rope should be correct, here are some ideas for a fix:
1) like someone suggested previously, sewing another layer or two of fabric around the problem area will make it thicker.
2) (I recommend) Have the trampoline modified by cutting a rectangular section off the corner, removing a 6 - 8" section of that bolt rope, of the trampoline where it pulls out and installing a grommet or webbing loop on the trampoline inset from the hull by a few inches. Install a plastic sail slug in the trampoline slot on that corner, feeding the rest of the trampoline into the slot normally, and lace that one problem area (using the bolt rope for the rest of the slot). The sail slug has no flex and might even survive long term if the slot is cracked. Do this on both sides while you have it removed.
Whatever you do, keep in mind that the more the bolt rope slips out of the track, the more chance you have to either crack it or extend a crack that may already exist. I would go straight to number two if it were me.
