Does it happen only if you play coop? and if you play it in single player its fine? it could be that the scenario command you use for camera or video has quant not enabled. not sure, if you want email me the mission
djsatane@gmail.com but thats only if it already works fine in single player mode but just have problems with coop.
PS... actually looking at the error it seems u have some wrong folder locations or something else misplaced in your mod because the error states page location multi_ingame not found, if this erorr only occurs with your modded or new mission then problem is somewhere with your mod if you get this error with all missions in game then you may have game thats badly patched.