I've got a circa 2013 MacPro (purchased January 2014). It's still my daily driver at work and still a great machine. Except when it isn't. I've had to hold down the power button to reboot it several times over the past few weeks when I get the "hypnowheel" mouse and the rest of the UI is unresponsive.

What's the current state of my diagnosis?

- This Mac has the low-end D300 video card, which wasn't covered by a recall that Apple did for other graphics cards. I never had these problems in the past.

- When it's in the "frozen" state, the ssh daemon is still up. I can log in, run stuff, see all my files.

- I was concerned that I might be looking at disk failure issues with my JBOD disk array. According to Disk Utility, all my SMART things are "verified" and I see nothing in the logs to suggest failures. Of course, modern disks go out of their way to retry and retry.

- I noticed that my Time Machine stripe wasn't connected this most recent time. This used to be a big and annoying problem early in the computer's life, but as Apple upgraded things, the stability of my disk mounting (via Thunderbolt 2) seems to have stabilized.

- My CrashPlan daemon, which I run on this machine, seems to be crashing. I'm guessing this is related to the terminal decline of their service. I doubt it's related to the wedging of the computer.

- Both recent freezes have been related to using Chrome. Scrolling, looking around, boom.

- The most recent freeze, I tried a thing I got from the Internet: unplugging and replugging my monitor. Black screen.

- I just did the PRAM/SMC reset. For grins.

Based on all of this, my current operating theory is that my video card is dying and/or recent Chrome upgrades are pushing on it in ways that tickle bugs in the driver or firmware. Supposedly, there's a sequel on the way, but it's not here yet. The iMac Pro isn't particularly attractive to me because I have a nice monitor already and would just want to swap out the computer part. The tentative path forward is to just suck it up and deal with weekly reboots. Not very attractive.