Probably can't help on this but in attempt to clarify exactly how this occurs...
I will clarify and have complete confidence you will do no worse than me ;)

Do you mean AI took control of city in previous AI turn, you then had your turn and then crash happened when you hit turn button, if so did AI take city from another AI faction or from you?
Or did you initiate battle to relieve seige within your go and lose city, then crash on end of turn?
The AI took control of it in the AI turn (obviously) and then the game came back to my control. Then, as I click the end-turn button the game immediately CTDs. The AI took the city from the player faction.

If when you're duplicating CTD, you're still same faction in same year, could there be anything to do with that - and city occupation co-incidental?
No, I bribed the city back to my control and no CTD. It then retook it (it was empty) and the CTD occured again (obviously not the same turn).

What factions are involved, and do they have any shadowing / hording effects active?
No hording or shadowing/shadowed by is active for these 2 factions.

Does mod have script? Anything to do with hidden resource / triggers for region?
No scripts. HRs and triggers have not been changed for a long time. This is a recent problem and I can only think that buildings and building descriptions and the DS file have been altered but as I said before it cannot be building related as the buildings all require 2 turns or more to build; and I have tested them all anyway.

I may have to play it through again and wait for it to reappear as I cannot work out what is wrong. If it occurs under different circumstances then I may be able to get some more clues.


Thx. for your interest - you're doing a fine job answering questions but I hope it is not taking you away from your own modding too much :)