I've searched on Google and here and can't seem to find much discussion about this, and what I do find is lots of people like me but no solutions. Freezing / Hanging The core problem is that ever since upgrading to High Sierra (or possibly the one before), my Mac Pro will experience several freezing episodes per day. I'm constantly losing work & losing focus. At least the hard restart happens quickly. The freezing or hanging is when the screen becomes completely non-responsive. Any audio that was playing will continue to play and the mouse can move around, but everything else is paused in time. No clicking on anything, video freezes in place, etc. My Machine & Peripherals macOS High Sierra v10.13.4 Mac Pro (Late 2013) Processor - 3.7 GHz Quad-Core Intel Xeon E5 Memory - 16 GB 1866 MHz DDR3 Graphics - AMD FirePro D300 2048 MB (two of these) 3 V243H Acer monitors at 1920x1080p Using 50% of my system hard drive storage Have 3 TB OWC Mercury Rack Pro connected Have a USB Expander taking a wireless Logitech MX Master mouse & my custom Ergodox keyboard + cables for a USB stick, phone charger, Logitech wireless gaming pad receiver And a Focusrite Sapphire Pro 40 audio interface connected, controlling all audio What I've Tried I've reset the SMC by unplugging the power cable for 15 seconds, plugging it back in for 5 seconds, then restarting. I've done the NVRAM/PRAM reset by holding option+command+P+R during restart. I've not been able to determine if any specific peripheral is the cause, since I need all 4 of the main ones for work and the rest are basically empty cables. I've also not been able to see a pattern in what triggers this to happen. The strange thing is this happened once or twice a day for months and then stopped for months. I stopped having the issue completely. But in the past two weeks it started back and has ramped up to as many times as 2 and 3 freezes / hang-ups per hour. Right now I'm on a couple hour spree of no freezes though. Any Insight? I keep updating High Sierra when they prompt me, except this last security update, because I'm hoping they fix it. It's been a few versions with no fix in sight and no acknowledgment that I've seen of the problem, despite the many complaints online. I'm pretty sure at some point I lodged an official complaint too, doing my part to notify them and send crash reports. I've tried to wade through the wiki posts here on MacRumors, read the official Apple support forum, applied my Google-fu search skills... I can't find any real discussion other than "try to reset the SMC/PRAM." Please help. I'm on the verge of bailing on Apple after waiting 3 years for a Mac Pro update and it never came, and crumbling to buy an old (current) 2013 model, only for them to update it soon after, and now my old (non-current) expensive 2013 trashcan model is plagued with freezing. The absurdity level has hit new heights for me. I just want to get my work done!