Jean Elcard
The Flavournator
What happens when the engine reports a error when trying to change one plot? Will that plot never be changed in the whole game, or might it be adressed afterwards again? Will ice remain on areas it shouldn't be after 1/3 of the game, or will it eventually be gone?
It will change, just not visually. If you mouseover the plot, you will see, what terrain it really is.
Would it be possible to do the all at once change, but somehow slow it a little down? If that would work, it might be a mix of both versions, too.
Sorry, impossible.
What makes me wonder is - why do some people have this problem and some don't?
Good question! Next question ...

I'm hoping that it is something else that is messing up the memory location of some plots under certain circumstances, not the engine itself. In this case, the error you get would be just an aftereffect, that would vanish, as soon as this other imaginary bug is fixed. What makes me think so is, that I noticed some other strange quirks, while I was checking out your save game.