I'm currently using Quake 2 Pro as the client and Quake 2 DOS as the dedicated server that running on the Maraakate's coop server mod with newly added maps. i don't believe that could be the problem due to changing the maps because of three occurrences the happen as to when this error appears.
The first occurrence is when a player exits the map.
The second occurrence is when the player votes for a different map.
And the third occurrence is when changing the map to a different map though the Q2DOS console. Now, when you mentioned running the gamemap command, I will be sure to use that for running such commands in the Q2DOS console.
I wanted to also mention that when I run the Maraakate's coop server on the alternative game servers listed: r1q2 dedicated, quake2 dedicated, yamagi dedicated, q2pro dedicated they also produce the wrong Game library is version 4 expected 3 and vice versa. I mention this because I presume there might be a possibility that I wouldn't get that FreeLibrary error message for those alternative game servers if they were to work without crashing and without producing the improper Game library version error.