Apologies for starting a thread for this, as I was unable to find a dedicated bug thread for V1.5. I got a Sigmar Preserve us with this in the error log:

mods/Rage_of_dark_Gods/data/world/maps/campaign/imperial_campaign/campaign_script.txt:
label_unit referenced non-existent army
11:36:31.205 [game.script] [error] Script execution error for <define_unit_group>, at line 2016, in mods/Rage_of_dark_Gods/data/world/maps/campaign/imperial_campaign/campaign_script.txt:
Error in battle script command 'define_unit_group': invalid unit label 'a6u1'
11:39:07.392 [system.rpt] [error] Sigma preserve us, Chaos has taken over!

I took a looksies at the campaign script but was unable to make heads or tails of it. The CTD occured during a battle as the Chaos Dwarves as soon as the requirements for this script were filled.

Thanks for your assistance