WMP12 + UHD Problems

Greetings!

I just received my new TV which sports a 3840 x 2160 Resolution and I was just testing some stuff when I already encountered a problem when it comes to watching SOME Video files:

Watching the Video File using Windows Media Player 12 in Fullscreen Mode:

While the right side plays fine, the left has this repeating blueish copy of the right one.
Sound plays fine too ( HDMI )

Watching the Video File using Windows Media Player 12 in Window Mode:
Working fine.

Watching the Video File using Movies & TV App in Fullscreen:

Working fine as well.

Problem with using the Movies & TV app is just that it's not doing terribly well with Subtitles of some shows I watch so I'd have to rely Media Player Classic as it too appears to be working despite being ugly as hell.

Out of curiosity I halved the resolution back to 1920 x 1080 what it used to be with my old TV and it works fine so it appears to be a resolution thing but that doesn't exactly help me in pinning down the exact problem xD

Any ideas how to solve this problem while watching Videos on 3840 x 2160 using Windows Media Player 12?
GPU us a GTX 780

Thanks in Advance =)

Answering my own Question I was able to solve the problem by increasing the resolution from 3840 x 2160 to the TV's native 4096 x 2160.
No clue why THAT fixed the issue though but hey... beggars can't be choosers =)