[LG 4K 49UF772V] Small black squares covering display on main LG overlay (settings, apps, etc) but HDMI input works flawlessly

[Virus17]

Hi all, I have this 4K LG 49UF772V TV which has had this issue since I bought it second hand and I'm wondering if anyone has any idea how it can be fixed as I am looking to sell it.

The issue: On the LG menu and main home screen + sub menus and programs such as Netflix, there are black squares all over the display which makes it impossible to use. However, the TV works flawlessly when using the display with a HDMI device connected.

I suspect this could be either a software issue since there's no physical defects with the display itself. The TV has the latest software update running (04.06.25). I've attempted to reflash it and downgrade it but I haven't managed to find a way to do it.

Also note that only 1 of the 3 HDMI ports work. The other two gives no output when a device is connected.

I have also carried out a factory reset and this has not made a difference.

I have attached a short video showing the TV connected to chromecast and the display working as expected and then pressing the settings button yields artifacts/small black squares. + some pictures showing this.

Thank you in advance! 

LG_49.mov

[László Kiss]

It shines to be a receiver problem. This is practically a parallel module in the hardware with the HDMI pathes.