Troubleshooting guidance

[noctrine]

I am trying to force 1080p at 120Hz on my 2015 Sony KDL-50W800C LCD TV. GPU is an Nvidia 1080ti. My PC is connected directly to the TV via an 18 Gbps HDMI cable; audio is through a Denon AVR-S710W Receiver via HDMI ARC (also a high speed cable).

I tried creating a custom resolution in the Nvidia control panel; the "automatic" and "CVT - reduced blank" timing standards result in a readable display but there are significant artifacts -- thin horizontal lines scrolling across the screen and flickering rainbow horizontal lines at the top of the image. Also, there was frame skipping.

Googling around lead me to this image of "some guy's" timing settings -- when I input those settings it removed the graphical distortions but the overall display became mildly blurry. There was still frame skipping. Timing settings copied here in case the image link goes down:

Code:

Front Porch:   44       1
Sync Width:    22       1
Total Pixels:  2006     1083
Polarity:      +        +

I subsequently tried the CRU. The native and automatic LCD (standard/native/reduced) timing settings all had the same artifacts at 1080p 120Hz--and there was frame skipping.

At some point during this process the Nvidia control panel listed a 1920x1080 option under the "PC" section--and it was 120Hz by default! It worked, including audio, and no frame skipping, and I played Doom 2016 and Warframe at 120Hz briefly. Desktop fonts were mildly blurry but the games were fine. Now, for whatever reason, after rebooting, that setting is no longer listed in the Nvidia control panel.

This all seems like a timing issue and that if I knew the correct settings I could get this to work. How do I go about troubleshooting this? How do I recreate that 1080p @120Hz "PC" resolution that the Nvidia control panel had?

Thank you!