I've had this 3 times today:
I'm working, actively using my Macbook Pro in clamshell mode (closed lid, plugged in, 2 external screens connected with wired keyboard and mouse), and my screens close, the Mac locks (as if it goes to sleep, but the mac keeps going).
Alongside that, my wifi connection resets (ERR_CONNECTION_RESET) on all connected devices and stays down for a good minute or two. The router keeps broadcasting, all devices stay on the same SSID, but the connection to the internet is unavailable.
That is weird. What gives?