[Mobhack]

I noticed that the buggy terrain appears on the map edge only after smoke has first appeared on the map. Everything is just fine till smoke/flame is added.

If you press "U" to clear smoke, then the grass hexes that overwrite grey map edge ones go away again, until you press U again or new smoke arrives - triggering the global "show smoke" flag.

Now - if you clear smoke and then hit end turn, and no new smoke arrives - you might be able to make it through the turn end. However Don's solution of saving, exiting the game and restarting again is a much better solution here. Especially if you see some garbage map hexes that aren't green grass at the LHS of the map - like that red blob!.

So the problem seems to be related to the smoke, likely an index or a pointer out of bounds (?) - and the very large map with loads of toys on it - I'll need to debug that when I find the time. If it is (hopefully) in some small part then hopefully I can put some guard code into whatever is doing this and pointing off into the map array(s) which likely are declared just after the smoke one in memory. (If the game had been programmed in say Pascal, rather than C++, then that language would have thrown an array out of bounds error "hissy fit", C++ simply assumes that the programmer fully intended to do whatever daft thing it's told to..)