Turned out the problem was on my end: KazakiMod introduces some new scripts that don't play nice with this mod. I restarted using just Blunter but now I'm getting a crash on the Castle encounter that seems to be related to the American units that spawn in: the console says that am1 through am3 can't be found and the value TimeToAmericans is nil, and the game starts hanging after finishing off the 3rd (?) zombie wave until it freezes completely.