I want to create the databases on Linux, and then multiple users need to access the database directory. The other users are generally on Windows. You're correct, I'm not using the client/server architecture. (I haven't looked into it. If you think it's what I really should be doing, I can start to look at it.)
The C/S architecture ensures that no one can update the data in parallel. If there will be no updates, your setup should be fine (apart from issues like the ones you encountered..).