Scenario Editor Issues

The problem started happening after the latest update.

Whenever I go into scenario editor to create a map, the generated maps always have massive geometrical blotches of black throughout them, usually on water features. Usually the first map generated is okay, but any other maps seem to glitch. Whenever I try to edit the terrain the map also glitches like this.

I’ve tried playing around with graphics settings and nothing is working. Has anyone found a solution to this issue? It makes it impossible to use the scenario editor.