Experiencing this same issue. Friend is running linux and I am on windows. :( I wouldnt blame the mod author for not pursuing a fix. I cannot even imagine the amount of spaghetti going on with this bug.

For some reason Co-op with this mod breaks if one user is on Linux. Sounds like an issue with MCC itself. And yes, it does this if both players are also using Linux.

can confirm. am using linux and am lonely. (keeps desyncing)

My friend and were both playing on windows, same thing kept happening to us just now. We mostly noticed it occurring upon respawn of one player

I am using Linux, my friend is on Windows. It keeps desyncing / freezing.

Did y'all save & exit on every level? Its stated in the bio that it has to be done in co-op otherwise you'll experience desync

Same issue but both are on windows, this is not an OS bug. both using up to date game.

im having the same issue. Maybe its a halo update issue?

You're guaranteed to get a desync if you are on Linux and your friend is on Windows. This is a known issue with MCC and is not limited to Cursed Halo. It's actually an issue with a few different games.

The solution is for the Linux user to install the vcrun2019 redistributable into the Proton prefix used for MCC. The desyncs are caused by a slightly different implementation of some core libraries between Wine/Proton and Windows, and installing the official DLLs fixes this by making sure these core functions behave the same way for both players. Google for protontricks vcrun2019 - there's lot of guides on how to do this. Fixed all my desyncs (I installed both the 32bit and 64bit version, for good measure).

I'm experiencing this too as Linux with my friend on Windows. I'd played through most of this before with another friend on Windows, and another on Linux. Those playthrough's did not have this issue. I'm pretty convinced this is a recent update has the mod borked. Might be a good idea to verify if the vanilla campaign also suffers the same decent for a sanity check.

It may depend on the game, but the Linux/Windows desyncs are very very widely documented, with the root cause being inconsistent behavior between the Windows and Proton versions of ucrtbase.dll. Played with a Windows user maybe 2-3 months ago and ran into this; installing vcrun2019 on the Linux side resolved it.

Bumping this post, as a friend, who's a Linux user, is having this problem when we try to play this on co-op. vcrun2019 completely broke his MCC install.