Phoenix, I'm in the same boat as you with the same laptop but different monitor. At this point, it's either the g-sync locking up the laptop trying to communicate, or it's the hybrid thunder bolt/ displayport causing the issue.
I got three Acer xb270H hooked up to an EVGA displayport hub using a "cable matters" thunderbolt certified mDP to DP cable. The monitors come up, but all flash like a damn turn signal. If I go straight to one monitor using the CM cable, I get the same lockup you do.
I have two older Dell monitors that have DP inputs, so I tried all my cables and hub on those two and EVERYTHING worked as expected. Dual screen, no flickering, spanned, mirrored, you name it, it worked. So I know the laptop is fine (got it this week) and that my proof of concept using the dp hub can be used to output that to multiple monitors.
So then I got thinking, maybe I am just so unlucky that I got THREE bad Acer monitors. So I got out my old ultrabook and connected it to just one of the Acer monitors with no hub. Mirrored the ultrabook right away.
So, cables = good
Laptop = good
Monitors = good
Hub = good
But, cables, plus laptop, plus hub plus monitors = turn signal. Go figure. Been working on this issue all week.