Originally Posted by
Baharr
Update: I fixed it!!! It feels incredible, like popping a zit you've had for months.
Turns out Med2 doesn't like "High Mountain" ground types being too densely clustered and freaks out, so I've interspersed them with "Low Mountain" around the problem mountains (i.e. the Hindu Kush/Himalayas) using GeoMod. They look less majestic but no longer phase out of existence when you scroll the map.
If you want to fix it for yourself, backup map_ground_types.tga in mods/ebii/data/world/maps/base, replace it with my version (attached below, unzip first), and then delete map.rwm in the same folder (the game will rebuild it when you next start a campaign). No idea if this is save compatible though, sorry.