Sony has promised to address the 4K/120 Hz issue affecting its XH90, XH900H, X9100H and XH92 TVs. The issue, which Sony has blamed on video processing, makes content at 4K and 120 Hz look blurry.
https://www.notebookcheck.net/Sony-promises-to-address-blurry-4K-120-Hz-issue-on-XH90-XH900H-X9100H-and-XH92-TVs.504369.0.html
See the latest update on the issue:
IMPORTANT: This article applies only to specific products and/or operating systems. Check Applicable Products and Categories for details.
There is a software issue in video processing when using the TV in Game/Graphics mode.
12/02/20: Firmware update version v6.0414 is now available for this issue.