Another observation I wish to make regarding the incidence of server crashes. GW4 would also crash, quite a lot, as much as SG4 when it was being run on the d.net server, yet for some unknown reason, when it was run on DieHard's computer, it would not crash anywhere near as often. We never did figure out why this was the case.
Bonk has identified an issue with the shiplist, not all eras and hull classes actually have ships for the server to use. This causes problems with the server and is a known factor of instability, I am told they will rectify this problem.
Good work for figuring this out.
I would also suggest trying to duplicate the SG4 server on another computer, perhaps Bonk's or DieHard's to see if there is a difference.