Tile Graphics Glitch

After a certain amount of turns (the specific amount varies), the tile outlines will glitch out and look like this:



The texture of the tiles can vary:



And as you can see, the current tech being researched is also affected, but that's not what I'm bothered about.


I'm running on highest settings in DX11 mode and my resolution is 1600x1200.

Any help would be appreciated.