after a full day of no crashes & even failing to trigger one by stressing the gpu (3d benchmark + streaming video + many browser tabs at the same time) it again randomly happened while web browsing tonight... but it actually recovered (w/display drivers disabled) without a sleep/wake cycle this time
so after some experimentation it seems to only happen with a monitor connected via the usb c-display port adapter. using only hdmi i have had no crashes, even at 4k 120hz. so i CAN keep it stable but at the cost of using my 2nd monitor...
hmmmm that gpu purchase is looming ever closer isn't it.....
@lion Weird.