flashing alpine trees and crashing mediterranean settlements

[makanyane]

no idea where to post this as don't have first idea what problem is... have been testing custom battle locations on a flat bit of test map set up to examine sparse woodland in each of the climates we're using.
Am running in a britannia based modfolder, with the descr_geography files intact using rebuild_geography_db = true
in the .cfg (EDIT: tested and it does same with those files removed)

climates: - tropical, higland, temp_coniferous, steppe, unused2, unused1 and temp_deciduous all work fine, but.............

custom battle location in Alpine climate with sparse_woodland groundtype gives me flashing trees!
it's hard to screeny flashing but if you compare the two images below you should spot trees in first which dissappear in second, this happens very rapidly even when camera viewpoint is static - it's a lot more than the sprite to model switch they are appearing and disappearing and I think sometimes re-arranging as though the game can't decide where to place them...



other problem climate is Mediterranean, normal custom battle there works fine, but if I try and add settlement through the custom battle menu, then I get CTD half way along loading bar... same settlements work fine in all other climates.

I've reversed out everything I can think of that I've deliberately altered regarding settlements and climate stuff - has anyone experienced any similar problems with these climates?

EDIT 2: further testing shows that the Alpine climate flashing trees thing happens in 'vanilla' british isles too, if I create large area of map with just alpine climate and sparse woodland ground type

the crash when trying to play siege battle in Mediterranean climate doesn't happen in 'vanilla' british isles (with climates tga switched to mediterranean) - so that one is down to something in my mod folder

BELATED EDIT 3: the problem with the Mediterranean climate was related to the length (too long and complex) of the path name for the captain's battlemap attachments texture --- really, really, don't ask me why! - or why it only affected Mediterranean sieges.... :doh