Terrain mangled up in classical map mode

Does the development team have any plan to solve the bug in classical map mode where the terrain is mangled up and the wrong terrain icon is shown? It's been around for several months now... it is fine on load, and then when playing for 5-10 minutes, it looks like this:

The "wrong icon" can be any pic used in the game; here it is a heavy tank and a city, but it could also be a country flag, a resource symbol, etc etc.

Since the new map mode can't properly display terrain either, we now have no more way to get a clear overview of the terrain of a region. Please fix urgently.