Q90T 4K @ 120hz Not available on port 4 (Game Connection)

[Sni9er]

Hey folks, a little stumped here

Running W10 PC with EVGA 2070 Super into port 4 (game port) on my Q90T with an Amplifier on Port 3 (eARC) the control panel will not display 4k@120hz (input plus & game mode enabled) the highest refresh I can access is 1440p@120hz

Curiously however if I plug the computer into port 3 on the TV I can access 4K@120Hz I thought my problems were over but now my amp is on port 4 (or any other for that matter) eARC is not supported so I have no audio...

(tried 2 different 4k/HDMI2.1 Cables the issues as described is repeatable)

can someone shed some light on this peculiar situation I find myself in?

[Zippycelt]

I get 4K@120hz hdmi 4 only sometimes depending on the game ( only one so far in pS5 ) and that was after changing a bunch of settings in ps5 plus toggling game mode on TV which I found in a Sony forum. 

im using the Q80 model 

as usual all a bit of a faff 

my friend as LG and all just works automatically 

[Scarhead]

Same problem here, no 4K 120hz on port 4 only on port 3 with nvidia card.

I tested deactivating HDR, lowering color to 4:2:2 and 4:2:0, changing gamemode settings, deactivating Anynet+ but no luck.

Any suggestions?