Mac Pro freezes and reboots after sleep

[slylandro_probe]

I've been having some strange issues with my Mac Pro over the last couple of days. It seems that after it wakes from sleep, it restarts. But this is not a soft restart and it is not due to issues such as this.

The symptoms are as follows:

1. Wake from sleep. Monitors turn on, everything seems normal at first.
2. Then, everything freezes. Can't move the cursor, keyboard input is ignored, etc.
3. All of a sudden the monitors turn back off and after a few moments, I'm greeted with a boot screen. The system has evidently rebooted, but it was not a soft restart because I have verbose mode on and the system displays text output when it shuts down. Since the monitors turn off and then the system is suddenly on again, this smells much more like a power event than any kind of software issue.
4. Furthermore, there are no kernel panics in /Library/Logs/DiagnosticReports. The only indication of a restart is a BOOT TIME message in /var/log/system.log.
5. I get no help from tricks such as this:

$ log show --predicate 'eventMessage contains "Previous shutdown cause"' --last 24h

That just yields:

log: warning: The log archive contains partial or missing metadata
log: cannot use --last when archive metadata is missing

So I'm totally at a loss as to what specifically is causing this power event and abruptly restarting my system after sleep. This has happened 2 or 3 times so far over the past couple of days.

What really worries me is that I've had to replace the power supply in my Mac Pro in the past year or so. My previous one went bad, I think because of old age and having too many things plugged into my Mac that were sucking power. My current one has been used, so I'm worried that it's reaching its end of life as well. There's no way to test power supply health AFAIK (although I did come across a post recently on Electrical Engineering Stack Exchange which discusses the possibility of this).

So what could be going on? I'm really not sure what to try at this point, other than to keep my Mac awake, which increases my electric bill.

 

[applCore]

Have you tried to simply stop the system from sleeping for a period of time to see if the problem goes away? I realize you may use more electricity, BUT doing this for a couple of weeks (I guess you'd want to do it for a little longer than the amount of time you've seen these issues so far) to see if the problem repeats when you take power saving/sleep out of the equation?

I personally had strange troubles before with sleep involved and I had enabled screensavers (not exactly the same as yours, but my system would hang) and I disabled screensavers and the problem never reared its head again as I found the window manager was struggling coming back up at certain times after the screen saver had engaged.

 

[slylandro_probe]

Have you tried to simply stop the system from sleeping for a period of time to see if the problem goes away? I realize you may use more electricity, BUT doing this for a couple of weeks (I guess you'd want to do it for a little longer than the amount of time you've seen these issues so far) to see if the problem repeats when you take power saving/sleep out of the equation?

I personally had strange troubles before with sleep involved and I had enabled screensavers (not exactly the same as yours, but my system would hang) and I disabled screensavers and the problem never reared its head again as I found the window manager was struggling coming back up at certain times after the screen saver had engaged.

I'll try this for the next few days, maybe even a week or two. Yet, I'd still like to know what might be going on in the meantime.

 

[slylandro_probe]

So I've followed your advice, applCore. My system definitely hasn't had problems over the past few days now that I'm keeping it awake constantly. At least I've now isolated that sleep is in fact the issue, but I'd prefer not to keep things this way. I'd like to be able to sleep my machine again... I just need to find out what the specific problem is.

 

[slylandro_probe]

So for about a week, I went without sleeping my computer. For the past few days I've slept my computer about 4 or 5 times. On this last time, my computer rebooted abruptly again, after about 5-10 minutes or so from waking up. So there was a delay this time, wherein my computer functioned normally.

The symptoms were the same. Clean logs, no shutdown text, a clicking sound that sounded like my power supply. This time I was also lifting and bumping some things around my office. Heavy things. My colleague wondered if the bumping around somehow caused something in my computer to shake and thus reboot. I tried to reproduce this by shaking wires and kicking the side of my computer (not hard kicks), but nothing happened. Very strange stuff...

 

[slylandro_probe]

Well, after upgrading to Mojave and replacing my old video card with a Radeon RX 580, the problem seems completely gone. I've slept my computer at least 14 times since upgrading (once per night, maybe more) and I haven't noticed any problems in these 2 weeks. So, I consider the problem solved, although I'd like to know what originally happened on High Sierra if anyone has that insight.