Vizio TV has wrong native res. on Windows

[wintercat]

Edit: solved. I have no clue how, but the issue just fixed itself, seemingly for good, while I was fucking with it some more.

 

I have a Vizio e50x-e1 3840x2160 TV I use as a third display on my battle station for twitch, movies, and couch games. I've had a really weird issue with it since I got it. When I'm plugged from my GPU to HDMI 1 on the TV, the native resolution for the TV in Windows display settings is 4096x2160. This means I get a little bit of squishing/stretching and if I instead set it to 3840x2160, I get letterboxing on the left and right of the display. On other HDMI inputs it behaves normally and the maximum allowed resolution is 3840x2160. HDMI 1 is HDMI 2.0 (ARC), the others are HDMI 1.4. My GPU is an EVGA 1070. My other monitors are 1920x1080 Acer's, using display port to HDMI cables. I've factory reset the TV, checked for firmware updates, dug through the picture and input settings, I would like to use HDMI 1 on my TV since my understanding is 2.0 allows for 4K @ 60hz. I just don't understand this weird resolution issue. Has anyone else run into something like this or have any ideas for what could cause it?

Edited March 8, 2018 by wintercat