Only a few clients can join our server as most are instantly kicked with the error "Steam Ticket failed"

The server does not require addons, and all of the guys I talked to could connect without issues, but others seem to get booted everytime. We are running the game as a client through steam, the server uses the command line updater executable to keep the game up to date (steamcmd.exe).

I read that using a launcher as a client causes this issue. Interestingly I cannot find any feedback on this tracker from a server side perspective.

I won't post our server IP as this could be seen as promotion. However, I'd like to gather some feedback if this error is common or something specific for our server.