Poor Multiplayer Performance

I've been playing Satisfactory on my dedicated game server for a few days now, but the performance is sometimes so bad that it's really annoying. We have the problem that the conveyor belts stop from time to time or are extremely rubberbanded. The trains have exactly the same problem...It looks like a network problem (rubber banding) but I can't imagine that our internet connections are too bad. We both have 100mbits+ and my server is at Hetzer (big server provider) with 1Gbit. We have already tried various network settings, both ingame and individual things in the Satisfactory Config files. I also use AMP for hosting...have I overlooked something?

When you are alone on the server it works fine, but as soon as a second player joins it gets bad.

The thing that surprises us is that we have already played on the same server in Early Access and with even more people and it ran without any problems...