Happened to me once in 4D1. No mods or anything, it was a home server.
We finished a TDM match in mp_boneyard and the next map was mp_compact, but my game loaded mp_boneyard once again, while the rest of my friends had salvage on. Weird thing was (as seen in OP's video), you can see the other players' movements and hear sound effects from the map which loaded for them, but you're still in a different map :shock: