Hello, I have been having a very annoying flicker on the bottom 25% of one of my Asus PB278 monitors. I recently upgraded from a GTX1080 where I never had this issue. I've had these monitors since 2012 with no issues till now. I have two of the same model monitors side by side and it only happens to one of them. You can see 1 frame flickers in the video @ the timestamps on the right monitor only.
Video link: https:// streamable (dot) com/yhwsch

 
This issue however does not happen when I use HDMI with the problem monitor, everything is okay with HDMI.
So far I have tried the following:
- Swapped around 5 different DP cables 1.2 and 1.4
- Tried all 3 DP ports on back of GPU
- DDU'd drivers 3 times
- Toggled G-SYNC on/off
 
Even after trying all the above, I have the same issue on the same monitor at the same spot. I am unsure of what to do at this point.

Naur1
Do you still not have the old 1080 to test?  

I do have the 1080, but I literally installed the 3090 few hrs ago, was on 1080 before that and it was working perfectly.

Naur1
I would install the 1080 again just to be 100% certain, doesn't take long.  If it fine, then you have bad DP ports on GPU.  Try different DP port on back of monitor if it has more than 1 port and test only 1 monitor hooked up at a time

I have only 1 DP port on back of monitor, but I have connected it to all 3 DP ports on back of GPU, same issue across all 3 DP ports.

Any updates on this? Are you still having the issue?

I've avoided the issue by running at 240hz and turning Gsync off for now.