Sorry for not getting back to report this sooner; stuff I had to do yesterday wound up being more complicated and exhausting than I expected, so I didn't get anything at all done on the computer when I got back (mostly I hid under a blanket and fell asleep).

but it's actually a bug in older versions. Game->SetComboSolid() treated maps as being numbered from 0 instead of 1. Every other function got it right.
I vaguely recall thinking that was weird! ...multiple years ago when I made the original version of the water boots, that is. That perfectly explains why the cliffs are getting changed.

I think the order of my quotes to the screenshots is mismatched (the one with the cliffs and leevers is showing the combo that got changed unintentionally) but it sounds like this mystery is already solved.

This will probably be handled with an extra rule, meaning it will depend on the version the quest was saved in.
That sounds like a good backwards compatibility fix.

Do you still want a copy of my quest for anything related to this? If so, I can send you my current prerelease (which is still the one I was testing this stuff in). The actual release version will also be out in a few days, and I have no intention of passwording it.