Plutonium

Yesterday, a friend and I tested out the campaign coop mod to see if it would work on Plutonium yet and to my surprise it did, but we encountered two problems that made most of the experience unplayable (the following problems were only experienced by whoever was player 2).
On one hand, every mission with the exception of Vorkuta, Project Nova, U.S.D.D, Numbers, Revelations and Redemption cannot be played due to the game displaying an error that says:
"CGAME_SERVER_WEAPON_INDEX_MISMATCH"
And on the other hand, the mission Rebirth would straight up cause a crash from DirectX encountering an unexpected issue.
If anybody could explain to me what exactly causes these issues, that would be greatly appreciated. Hopefully the Plutonium devs can become aware of these problems and solve them at some point.
Here is the mod in case you want to verify the issues yourself or have fun with your friends on the few missions this works on currently:
http://se2dev.com/2017/06/black-ops-coop.html