Second monitor flickers while connected through HDMI

[ofiridan22]

System: Windows 10
Battery or AC: Both
Model: S510UQ (X510UQ in dxdiag)
Frequency of occurrence: One in a couple of minutes
Reset OS: Yes, didn't help
Screenshot or video:
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Detailed description：Every second PC monitor I connect through HDMI flickers or turns black and reapears again after a second. I tried to update the drivers, change ever power settings to Maximum and reset windows and it still happens. I have two "graphics cards" - intel HD 620 and NVIDIA GeForce 940MX.
I wonder if there are any other S510UQ owners that faced the same issue.
It started about a year ago.
Appreciate your help.

[ofiridan22]

An example of my screen when it turns black and reappear again.
It also flickers once in a while (no pattern that I could recognize).
It flickers more often when the CPU is working hard.
The cable, pc and electricity are all fine. I checked this setup with two other newer ASUS laptops and they both where OK (no flickers whatsoever).

[Blake_ASUS]

Hello ofridan22,
Please kindly send the device to our service center for further examination.
Sorry for the inconvenience caused.
Thank you.