Hello Cybermind.
I had this problem when using Multiplayer commands in my last online multiplayer game too.
The server app (made in AppGameKit Studio Tier 1) seems to stop responding to connection after 3 days. Need to be restarted.
But after a couple of weeks, the server app seems to be able to function for 2 weeks before it stopped responding to messages, and need to be restarted. I didn't do anything, it just improves on it's own.
The server was hosted in Amazon AWS, using some sort of Windows virtual machine I think.
Aside from using Multiplayer commands, it also uses File OpenToWrite() commands.
I think, there are 3 possibilities regarding the source of the problem, but I cannot confirm them:
1) Amazon AWS is doing some backend restarting on their server or something similar
2) There's a bug in my server app, where if a client is sending a near-empty/very small file size (1-3 bytes?), the server will OpenToWrite() and never CloseFile(), due to my incorrect programming. This probably introduced some kind of bloat, and make AppGameKit server app stop working correctly after a certain threshold. AppGameKit apps will throw some weird unnamed error if it deals with RAM problem, whether it normal RAM or VRAM, you can't always see what it is. The app will still run, but they'd not function correctly anymore.
3) Another one of many AppGameKit hidden internal bug.
Not sure if the above is relevant to your case.