I tried to expand the map of RTW 1.3 vanilla as follows: (also tried in 1.0 with same CTDs)

Placed the original map in the upper left corner of the new tga files, and filled the rest with ground colour:
RGB (5,5,5) for map_heights.tga
low fertility ground for Map_ground_types.tga
mediterranean climate for map_climates.tga
RGB (0,0,0) for map_features.tga
in Map_regions.tga the new places were added to an existing region (Elymais, Susa)
map_trade_routes.tga, map_roughness.tga and disasters.tga are all black (0,0,0)
water_surface.tga is the original file

I applied the new size of the map in descr_terrain.txt (343,218) and created <my_campaign>_regions_and_settlement_names.txt as a copy of the imperial campaigns file. All other files are left unchanged.

When I try to start the campaign with any of the factiont I get a CTD with no error message, the loading bar is not reached and a map.rwm is created.

This issue is probably not created by characters, wonders or resources got placed on inpassable terrain, because that ought to produce a different error.

Can anyone please help how to fix this?