I'm afraid I have no answer, but also experiencing the same thing. I have a MacPro 6,1 (I know, pretty old...) and it crashes with the panic multiple times a day (only 1 today so far!) "panic(cpu 2 caller 0xffffff80149f9a25): userspace watchdog timeout: no successful checkins from com.apple.WindowServer in 120 seconds" I wanted to mention some basic things I've tried: Disconnecting external HDD Disconnecting my LG ultra-wide monitor Disconnecting my (oooold) DELL monitor Changing fan speeds using TGPro (felt like it was doing something useful, but I wasn't convinced it made a difference) Just using 1 app at a time (e.g. Chrome, Outlook) I can spend hours editing photos on Lightroom or doing sound Editing on Cubase and it can be fine. It feels random. As much as I want to blame the Microsoft Products I've got, it seems to crash when I'm dragging something, or switching desktop a lot, especially if I'm doing lots of things at once. It feels like it can't keep up, even thought the machine is very nippy generally. The screen will freeze but the mouse will continue to work for 30 seconds, then everything freezes for the remaining 90 seconds until it resets itself. Feels like GPU issue, but I'm no expert. So much for 2 graphics cards being useful huh? I'm waiting for the new macs to come out, but scared that this is an OS problem and it will continue! I didn't have this problem on my 5,1 Mac and seriously considering going back to it. Good luck to all of you (us) in getting over this ridiculous unreliability of what was a much loved brand for me.