LG OLED c7t 55inch screen has horizontal band can ON for a short while

My LG OLED c8 55inch screen has horizontal bands can be ON for a short while like 15 seconds and it will go black screen, hardly have enough time for me to do anything during that short screen-on time

when it is black, seldomly if I press select source then it can show the screen with horizontal band again for a short while like 15 seconds and will go black screen again

I have tried:

1) Clean all the cable connections

I see some youtube videos about taping some parts of the cable but I don't know exactly which cable to tried because it looks different in my model from the video, so I just tried on these cables:

2) Baking the main board in oven at 200 Celcius degrees for 10 mins

But that is the best I can get and still cannot bring it back to normal.

What else could I tried?

Here are some more photos for your references: