It would make sense if none of the players showed up, but only 7-8 of the 20 seem to be missing.I started one of these games and had exactly the same problem when I tried to add unassigned players.
I am obviously doing something wrong but any player I add to the database only seem to show up if assigned to a team.
Let me see if your previous suggestion has worked. If not, this will be my next step.Perhaps it is possible to add a trial-contract to the players to a random club, for 1 week or so from the start? That way they won't be attached at least, but it might make it more likely that they sign for that specific team.