Macbook freezes during compile

I've had a new macbook pro 15 touchbar, 16GB/512GB for about a week. As a seasoned developer I installed high sierra (and have updated since, including this weeks update). I have other machines I can use. I'm new to macOS, but experienced in *nix.


I'm currently working on an Apache OpenSource project (Atlas) which is java based + maven.


I was on a conference call today using zoom.us, with the system connected via USB-C to a 4K display. keyboard/mouse was bluetooth. Internal webcam was in use, and the meeting had about 16 participants, 6 on video.


During the call I decided to download a patch & rebuild the source code - resulting in, as expected, high CPU & high I/O. After a few minutes I noticed the compile seemed to hang, as did the zoom video. The zoom audio continued. The clock stopped. I couldn't raise/lower any windows & noticed the cursor was the "text insert" cursor. I couldn't use the menu to get to force quit, nor cmd-option-ESC. Fans continue to run fairly heavily suggesting perhaps the system has got into some UI or kernel loop... though after another 10 mins or so slowed down with no change to the UI.


Any ideas?