Thanks for the offer

The script was the only thing that I changed that moved the date of the CTD (changes also made it more frequent). I've got as far as narrowing it down to a set of spawns for one of the factions (by deleting big chunks of the script so that's all that's in it and its still crashing) it definitely doesn't occur on the exact turn they spawn but a while afterwards, so I think my hypothesis about it relating to getting two armies on same spot and problems when AI moves them might be right. Think I'm getting close to answer so will keep testing for a bit (then probably ask for help again!).