To clarify what you are seeing. by stupidly fast do you mean it happens one time and lasts a short length time or do you mean its happening at fast rate many times? does it look like a flicker in brightness, or does it look more like the screen freaks out and comes back after like a tenth of a second.

test solution
since this forum has seen this many of times recently, wait till it starts happening again and you know it will continue, then change your monitor to 60hz . your eyes will suffer for a time being at the measly 60fps but if it fixes your issue buy a new cable or swap it with one that you already have. DP 1.2 or higher.

My cable along with a few other users have reported their original cable from the box going bad. I think ASUS cheaped out on the cable that was included.Also, To explain why the flicker happens mostly in Desktop and not in games is due to purely the number of frames/data being run through the cable. Your desktop is going to use the most bandwidth on the cable due to it being a solid 144/165OC FPS with no drop in frame rate making the desktop needing more bandwidth than games. Games you will see a varying number of FPS usually not pouring out a straight 144fps through that cable. If the 60fps change fixes the flickering issue the solution most likely is a new cable.