Before you say " You have got to run the game BEFORE you mount it " I know, before I mounted, I play all the games for about 1-2 hours before mounting. I have tried other fixes to, do not work.
So as soon as I mounted it I restarted GMOD, and then tried to run Ineu Pass in SinglePlayer this happens.
Goto your steam library, rightclick the game and goto propeties. Then click BETA and make sure the Steampipe beta has been selected.
I know, I already looked at that thread, still does not work.
Send me your console log history from the beginning to the point where you have joined that map and walked around for a few seconds.
Try to disable ALL addons.