If you have subscribed to this on workshop and load this up on your own pc with command map workshop/531384846, there is an issue with navigation and the bosses do not move. Same applies to servers that try to run this map from the workshop.

It appears that nav (navigation file for bots) is not read upon loading the workshop map and the bosses that rely to this, cannot move.

So in order to properly get it to work on your own pc, go to location:

STEAM\SteamApps\workshop\content\440\531384846 (might be different if you have changed the path ingame)

and copy the file from there to:

STEAM\SteamApps\common\Team Fortress 2\tf\maps

Then simply start the map with console map pl_millstone_event

Download the separate .nav file from here: http://server2.pelipurkki.fi/~dustin/tf2/pl_millstone_event.nav

Place it next to the same maps directory, here:

STEAM\SteamApps\common\Team Fortress 2\tf\maps

This will properly load the navigation file instead of it borking and not loading. You can also load this map on a dedicated server same way by just using the bsp file instead of workshop, since it's broken until Valve will fix it, if they ever will. However, if you do this on a dedicatd server, map will not redownload to players when new version is out, since it's the same name as the one before. I would not recommend using this on a server before it's done.