I've had my PX75 since early September and upon installing it, that is transferring the HDMI cable from my P75-C1 to the new PX75 had device compatibility issues when turning on Full UHD Color setting on the PX75. Everything is routed through my Denon AVR-x4300h.
My list of problem devices are: Tivo Bolt+ DVR, Oppo UDP-203, Nvidia Shield ATV and now even Roku Ultra.
They all experience interment Black Screens, sometime even loss of video output and audio issues.
Disable the Full UHD Color setting on the PX75 and all is good but of course no UHD Color support.
Tried directly connecting each device directly to the PX75 again mixed results - no solutions.
Even tried a HDFury Vertex2, great support by the way but could not fix the problem devices.
The only temp solution I found was a borrowed jailbroke UDP-203 and it played all UHD discs and looked beautifull.
Called Vizio TS the first day and got the usual basic support, ended up calling several more times until I got a call back from Teir 3 support acknowledging some device compatibility problems and they were working on it.
Talked to Teir 3 a few weeks latter and still no ETA for a fix. Am now at 7 weeks and counting.
OK, Now if your panel looks good, little or no Color banding and acceptable DSE I would suggest calling TS and pushing them for a firmware fix. Replacing the TV generally won't fix these issues
This of course assumes that using Smartcast, viewing Netflix or Vudu playing UHD material looks good.
Full UHD Color setting is only use for it's HDMI inputs and not needed for Smartcast the apps.
All of this indicate they are having problems when negotiating correct formats between some devices for UHD video settings, Color Space and bit depth(8bit, 10bit and 12bit).
Remember that depending on the devices can be good for a little wile and due to change in formats, such as when playing a UHD Disc jumping from menu to playing can trigger this type of issue making it visible and even changing channels on a cable box or switching to commercials can trigger a new negotiation.
Vizio PX75-G1 | Vizio P75-C1 | Denon AVR-X4500H | OPPO UDP-203 | Tivo Bolt+| Nvidia Shield Android TV | Roku Ultra | Apple TV 4k | C =Axiom VP150 |FL/FR =Axiom M60 |SL/SR =Axiom QS8 |TFL/TFR =Bose 161 | TRL/TRR =Bose 161 | Sub =Reaction Audio S-15 500W SEALED SUBWOOFER