Question Higher refresh rate, display error

Sep 22, 2021
I have an AOC 27G2U monitor and Palit RTX 3070 Gamerock Oc gpu.
And i have a display issue when change the refresh rate to 144hz.
It has about 10 cm black screen from the bottom and 2-3 rows green/blue pixel error.
But if i change it lower refresh rate maybe 75hz it works normally.
And now i don't know which part cause the problem (The gpu or the monitor).
I tried this variations for testing.
-Tried with different display port cable and hdmi cable.
-Tried with bootable linux ubuntu os.
-Tried with just 1 monitor (without my secondary).
-Updated vga driver to the latest.
-Installed the monitor driver from the aoc homepage.
-Tried different ports in the gpu.
And now i don't know how to test it which part is the faulty component or maybe it is software error :(.
Unfortunately i can't test it with other pc to plug the monitor , or change the vga in my current pc :(.
So if anybody have a tip what is the problem i would be extremely thankful.