The in-game server browser appears to be lying to me reporting "Full" with 12/12 as I knew via Steam info there are free slots. This has been an issue since I modded my server. Depending on where you look it will either report true or false numbers. Steam Server browser will report "True" but game info will report "False" numbers while showing "true" if you manually count the number of names as queued don't show.
This is due to it counting players downloading required mods. It's a problem not isolated to the game as this has set off a tripwire with my server host. They seem to have corrected this by drawing on a different info source from Steam which might be helpful hint to a fix this on your end.
This is of concern as it deters people from joining. TIA.