One Side of Samsung TV Screen is Darker than the Other

Can anyone help shed some light on the problem below? (pun not intended)

I've copied a photo and the model # below but basically the other morning I noticed the left hand side of the screen is now darker than the right hand side. It seemingly occurred overnight and all that changed recently is that one of the inputs (Sky TV) has gone from HD to UHD for some channels but I don't think that would have any effect here.

Model: QE43Q60RATXXU

It appears to be coming from the bottom edge on the LHS, I've tried multiple different inputs/HDMI cables and factory resetting the TV but to no avail as well as tinkering with all of the display settings themselves (inc all automatic dimming etc). The TV is ~3 years old so most likely out of warranty but still not so old you'd expect the panel to start failing.

If anyone has any suggestions or can help diagnose the issue before I take this further with the store/Samsung it'd be great. Popular opinion based on googling seems to suggest the backlight LEDs fading but I would've thought a more significant portion of the screen would be effected if this was the case.