S2721QS, DP flickering issue

Hi all,

I have just received my S2721QS and now connected two laptops on it. I am having an issue on HP Laptop connected via dock with DP cable. It's flickering sometimes constantly, sometimes once in a while.

Here is a video of it: https://drive.google.com/file/d/1A6lKAkRwND7ctK9gVu9lZJV34sstSklQ/view?usp=sharing

Things that I did to solve the issue:

1- Unplug all the cables and plug again one by one.

2- Updated HP laptop graphics drivers.

3- Installed Dell driver and tray application.

None of that worked. I read in some discussions to turn DP 1.2 off, but couldn't find it in my monitor settings. Can you help me on this?

Thanks in advance!