I may have found a workaround, its possible that units assigned as an "_aux" caste type don't get looked at by the civil war scripts. So this could fix the issue! I need to do some more testing....been testing civil wars for 4 days

Going crazy
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Edit - Updated the fix pack with hopefully another fix for civil war crashes. In theory newly spawned civil war armies should work now. They will still have reform units in them, sadly. I may see what I can do about that. For now the GC still has 2 parties to start, not sure if we will do 4 or not (I think you gain parties as you grow now).
I think this fix may also have fixed current save game civil wars too.