(I am not sure where to write it. But I think it is still related. It is not only Experimental but also standard server.)
I often play behind an always-on NAT. Sometimes when 'transfreing game', the internet connection gets crowded and the download freezes/stalls at some point. Then I kill simutrans.
At this point, maybe the server think that I am still downloading and waits for response from me. The server pauses until I finished download, which will not happen because I killed simutrans. The server thinks it still connected to me, which in reality just the NAT server.
Then the server waits for looong time...
The server runs again after a few minutes, sometimes hours, or sometimes even the server needs to be restarted manually. Timothy once needed to restart the server because of this. Never happened with deMangler's so far as the savegame is usually still small.
Maybe we need something like timeout...