Well, for starters, I'd let the IT professional in on how to use the Admin Console and command line for server. Rebooting the server without shutting down the databases is ... BAD. You need a server admin who's at least familiar with FileMaker; otherwise, you're risking some serious damage to the databases. (Hopefully, you've already done this.)
That aside, if the server process is freezing (literally unresponsive), you can look for a few things:
1) Is the RAM cache the right size? (I had a contact at DevCon who mistakenly thought that increasing the RAM cache to match the server's available memory would make it run better. He had the same problem you're experiencing.)
2) Monitor the memory of the server process itself. Is it basically stable, or is it increasing over time? If the process keeps increasing its memory usage, you may have a memory leak problem. Just because the server has "adequate resources" doesn't mean the process itself doesn't have issues.
3) What else is running on the server? Any mail services? SQL Server? Virus scans? (BTW - many server administrators either blindly include the FileMaker databases in the virus scans because they don't know any better, or stubbornly refuse to exclude them because of amorphous "security policy". This WILL result in corrupted databases, eventually.)
4) Are you using any ODBC connections to the databases? If so, how often are the databases being queried by external sources?
5) What server-side scripts are running? Any scheduled at the same time? The server-side scripting process used to be single-threaded (might still be; not sure), so if you schedule multiple sessions at the same time, they'll just queue up waiting their turn. This can cause memory issues.
Those are just some ideas off the top of my head, things I've seen before. There are others on the board here with more experience running Server installations who likely have other ideas to contribute.
One of my larger customers ...They are on Windows platform but I'm afraid I don't know much more than that about their equipment configuration.
Knowing the deployment configuration is almost more important than the development. The development cycle is always a tiny fraction of the life-cycle of the solution and as a community we do not put enough emphasis on that.
You do not ever want to get into a situation where you can not explain why your solution does not behave like your client expects it to do. But you have the be able to answer that question anyway,
That is CRITICAL. I can not stress that enough. You are not only responsible for the development, you are also responsible for making sure it RUNS RIGHT.
Ultimatly, the "does it run right" is what you will get scored against, not the "oh well,it runs right on my machine..."
Thanks for all your suggestions. We did add a server side script - single, not scheduled - so I will be looking into that in particular. There is no ODBC connections from my solution and they are not using the server for anything other than FM Server. All the other suggestions however will be looked into!
I have a similar problem here, with a fresh installation Windows Server 2012 and FileMaker Server 13.
Randomly, the FMSE (FileMaker Script Engine) stops working (script report: unexpected stop)
I need to restart the FMSE via command line, when it happens.
My problem persist...
Possibly check for automatic updates causing a reboot of the machine?
Do you know if the server hardware rebooted or it was just an FMS process crash?
Do they reboot the server on a schedule (echoing memory leak comments)?