Network Sharing Dies Constantly I posted this on the Apple forums but, as usual, it goes weeks and weeks without answers.

I have strange problem that has happened before but now is many times worse.  The issue is that I have a Mac Mini running High Sierra and it will stop publishing its shares to my network after between an hour and four hours (I haven't nailed this down exactly) and every one of my Mac's, regardless of OS version, will be unable to access the shares anymore.  If I try to connect to that system in any way from any computer it just tries for a few minutes and tells me it is unavailable.  One interesting additional issue is that when the computer stops publishing shares I can also no longer access the sharing preference pane, always getting the message "Preferences Error - Could not load Sharing preference pane".

This has happened before with much less regularity back when I had upgraded my "server" to El Capitan but it seemed to settle down eventually.

Coincidentally when this computer is in this "state" I can no longer shut down or restart, I have to physically power off the system to reboot it and get it to publish shares for another few hours or I can go to terminal and issue a sudo shutdown -r now and that will reboot it.

This may be unrelated but when this happens there is also a process i see in Activity Monitor that reports that "Login window" is not responding" which cannot be quit or force quit from Activity Monitor but can kill manually with a sudo kill in terminal (but killing  this and then it auto starting again doesn't fix the problem).

Before I erase what is my server (so thus a major issue to totally blow it away and start again) I wanted to see if anyone had some ideas.  I have booted into safe mode and gone into sharing and then shut down and I have reset the PRAM on the computer.

Today I watched Console as I tried to access the now-locked-up Sharing Preferences and did notice this message (not sure if this is relevant or not): 


  ERROR: _willSelectSemaphore timeout! (com.apple.preferences.sharing)


Update: Today I've been really logging everything and watching the system constantly and found that if I kill SMB and restart it then everything works again, including unlocking the sharing pane. I use: sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.smbd.plist and sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.smbd.plist

So it appears to be an SMB issue and I'm not sure what I can do to resolve it.  I did add a PLIST script to 'touch' the SMB process but have to wait that out to see if it does any good because it was actually a Mavericks fix that touching SMB would force it to restart.  I put it in Library/LaunchDaemon.
We are having the same issues since the last Server update, which deprecated file sharing, and relegates it to OS X (we have a mini). Besides the issues you are experiencing, it seems like we went back years in compatibility since High Sierra. 

All of our workstations are Windows 10. When we updated to 10.13, the first issue was anytime opening an AutoCAD file, all MS Excel links required us to acknowledge read-only, which hasn't been an issue in at least a couple years (but it's back). Then when we went to 10.13.2 and the corresponding server app, we had all the problems you mentioned. Additionally, our Windows workstations are slowing to a crawl. Issuing a save command from any application takes at least 5 sec in any application. Windows explorer (desktop and file explorer) crashes when it needs to copy/overwrite a file from the workstation to the server. It actually seems like it's getting worse each day.

Anyway, we've been doing this dance with Apple for 10 years and I don't think they are going to do anything. We just ordered a Synology DS918+ NAS to take over file sharing. I'll keep the mac mini server running Website and Mail until they are deprecated in the next OS X Server "update".