Disappearing Borders

[AA77]

So I've been playing this save for a while now and for quite some time now I noticed that some borders are disappearing from the map (as in the actual borders).
However, when I load a new game, all of the borders are back to normal.
I am running in heaven's graphical map mod but even after uninstalling that mod the issue doesn't go away.
I really don't want to start a new game now cause I like this save...
Is there anything I can do to fix it?

Screenshot to demonstrate:

 

[AndrewT]

Uninstalling mods does not remove the effects they have already had on a saved game; unless this happens on a game that's never been modded, there's probably nothing that can be done, I'm afraid!