RTX 3090 - Two Displays - Random flicker (on/off briefly)

[Classical Bets]

Hi,
I'm using RTX 3090 with two displays - one is AOC Agon AG32QCX (32' 144hz 1440p), the second is my TV ( TCL 75QLED860, 4K 120 Hz QLED). For some reason, when both are on, the TV is blinking, or turning on/off for like a second or two in random moments. Like if the cable was removed for a second. The monitor is connected through DisplayPort, and the TV is on HDMI.
I've tried various driver versions, game mode on/off, VRR on/off, changed the "Reported content" in NVidia control panel color settings to desktop applications, GPU on stock/undervolt, setting both displays to 120hz.
Cable that connects GPU to TV:
https://www.unitek-products.com/products/1-5m-hdmi-v2-1-cable?variant=37536780353711
I'm running out of ideas here - if anyone can chip in with suggestions, I would greatly appreciate it.

 

[Classical Bets]

How long is your cable? Is it 5M?

I have the 3M variant.

Almost certainly the cable quality, it's damaged / interference etc.
That cable should be ok but you do get iffy ones in batches. Does it work at lower refresh rates?

I'm yet to try it in 60 Hz, what I've noticed it flickers more frequently when the GPU usage it's high, but on the other hand it also does it idling on the desktop.