Problem seems to be known - cannot find a solution

Has anyone actually identified the problem and knows how to solve it? The server runs locally on my PC. Everything is set up as it should be and has been running flawlessly for several months now (always with the latest versions, of course).
Since today, I have had the problem that next to ‘Quit’ on the server it says ‘Player:?’ and ‘Ping:?’ and both my mate and I lose connection to the server after a short time. Sync doesn’t work (cars of others do not move). I have reset the server, reinstalled BeamMP and also reinstalled the game. No mods other than BeamMP are installed, and the port forwarding and firewall settings are as they should be and, above all, exactly as they have been working for months.

I keep finding reports about the problem, but somehow no solution. Can anyone say anything that really helps in Windows, or does anyone really know what the cause is?

Many thanks!

Is the beammp launcher up to date?