I just tried to load in and got a error. not sure if its one on my end cause i just started playing modded zombies today. but the error is:

server script error
cannot cast undefined to bool
Terminal script error
scripts/shared/flag_shared.gsc:0

I just tried to load in and got a error.

I suggest you try and verify the integrity of files through steam. Last person I talked with had a problem with the files of the game itself which was causing the issue. If you are playing with others, I suggest you both unsubscribe and then re-subscribe to the mod to try and fix the issue. Seemed like my several updates were causing issues for those with different version trying to play together. I'm trying to figure out if this is something on my end, but it only seems to be happening to a few players, so I think its potentially something wrong with the game files themselves. Possibly might have to uninstall and re-install the game itself. I also suggest trying to see if its only happening with my mod or is it happening when you try to load other mod maps as well?

Bro this map is so ass imo. I can't see ♥♥♥♥ with splitscreen due to the high graphics. Perks are hidden, bears are not that visible, challenges are unknown. I also want to throw myself out of a window without taking damage.