A current console can put out 4K at 120 Hz. Getting that to the screen means it passes through a cable, usually a receiver, and then the display. Each one has to be able to carry it. If any single link cannot, the console drops down, usually to 60 Hz, and carries on as though nothing happened.
The Cable
Look for a cable rated 48 Gbps. Under about three metres most decent cables manage. Above that, uncertified cable starts to cause trouble, and it shows up as occasional black flashes or dropped frames instead of a clean failure. That makes it hard to trace. On long runs we use fibre-optic HDMI.
The Receiver
Check which inputs actually support it. Plenty of receivers advertise 4K at 120 Hz and provide it on only two of their seven HDMI ports. Some early models had a known fault that produced no picture at all from certain consoles.
There is a simple alternative. Connect the console straight to the screen and send the sound back to the receiver down the same cable. That keeps the receiver out of the picture path altogether, costs nothing in quality, and removes a whole set of problems.
The Display
Confirm 4K at 120 Hz works on the port you are using, and that it still works with HDR switched on. Then turn on game mode, which switches off the picture processing that adds delay. The difference is easily noticeable in anything competitive.
Audio Latency
This gets less attention and still matters. A long sound processing chain delays the audio behind the picture. For films the receiver’s lip-sync setting corrects it. For competitive play, where hearing a footstep at the right moment counts, we keep the sound path short.