Problems appear to develop first with the game failing to perform a world save. I have notice that they will stop at a certain point. At that time, the ability to communicate with some part of Ark appears to stop. The CP no longer shows useful/valid info and appears to have no real connection to the running instance of the game.
You can stop the server from the CP, but it does nothing...game keeps running(still in the session list). If you can connect, doing a Cheat SaveWorld does nothing. Also tried a Cheat DoExit, which will eventually drop you from the server, but it stays running. Sometimes, you can continue to be able to reconnect after that.
Unfortunately, there seems to be no way to just kill the process, which is what is keeping a restart from happening. The only success I had was to do a full reinstall, which seemed to give me a new IP address, or just let it set for a very, very long time, and then some sort of divine intervention eventually happens; of course, those are many hours of lost play time.
I am experimenting with a server backup recovery, but that, so far, is just dragging on...and the server still shows in the session list. (update) But that only seems to restore the files(after deleting everything....so make sure you backup recent files, just in case) and does not force the game to stop while this is happening. So, another failure.
To limit role backs, I do backup all of the recent data and once I finally get to a point where I can start the server, I unzip what appears to be a good save and place it on the server in place of the older .ark file (just in case). Since you cannot correctly shut down the server, the .ark file will be whatever it was at the last restart. There are other ways to do this, but it is the method I use for now, since it is working for me. I think this is helpful when waiting for the divine intervention, so that you can ensure the server starts with the file you want to use when you are not present.
Of course, none of that matters if you cannot get to the point of doing a restart.
Sadly, I have lost hours and days of time on this (worse when it is one of the few days I have for playing). And, even trying to reach Nitrado by phone just gets you a 20 minute wait to leave some info. I just want someone to stop the game instance and I can handle it from there.