Philips 70PUS6724 Vertical "Banding"

Hello, I've got a Philips 70" 70PUS6724/12 second hand and recently it started showing some vertical banding. In some cases, it also gets very pixelized/washed out. I've already tried:

• Power cycle
• Updating the firmware
• Trying different picture modes (personal, vivid, etc)
• Trying different sources (Netflix App, PS4, Chromecast) in different HDMI ports and different configs (game mode on/off, HDMI Optimal)

For some colors the lines are not visible at all, I've run one of those backlight tests with different colors and it's mostly visible with black and dark grey.

I've read from some sources that it could be a T-con issue, which fortunately is like 10$ online. Any suggestions? The TV is not under warranty anymore.

I've also uploaded the TV demo, which looks amazing in the bright pictures, but weird in the dark ones.

I've been using the TV and it annoys me when there are dark backgrounds...