Its a BUG option, on the BUG general screen. If that save doesn't reproduce it there's not much I can do apart fropm go away and try to find a bug in the code by reading the code again I'm afraid. I've seen this symptom before (paths through water when it shouldn't) but I can't see how it can happen. Sadly all previous cases have also not reproduced from save games
Edit - BTW did it actually try to follow that path, or just DISPLAY that path? What happened when you executed the goto?
Edit 2 - actually I CAN see soemthing in the code that might be implicated. I have no reproducible test case but I'll fix what I can see in the hope that i might be the underlyin issue