After around 200 turns random developed tiles start appearing as blank muddy brown coloured tiles, have verified all game files, tried loading vulkan, changed to all different graphical quality settings as well as different screen resolutions with no solving this. With every re-load different developed tiles are affected, but the problem persists.

(Edit)

I have gone back through several load files and the problem isn't there in Early Modern and only seems to appear after advancing to Industrial Era. Since reading other similar posts the problems seem to have started with the latest patch.