We ran into this problem last Monday ( 4th July ) when I was hosting CanyonX, Gokart Raceway and the 57 Chevy mod. When I started the gokart track and the king of the hill canyonx derby, some players ended up somewhere us.
Then I got to thinking and ask if they had the 3 mods listed in the same order that I had in my Mods tab list.57 Chevy
and then CanyonX
Players that were having troubles, left the host and reordered these mods and rejoin my host and things were good for them now.
So if hosting with mulitable mods, I would suggest you list the order the mods are listed in your Mods tab in the host message, so joining players have the mods in the right order in their Mods tab when they enable them, so there no issue after joining your host.
Make thread a sticky, Janne?