TV swaps every 2.1s between normal and flickering horizontal scanlines

I have inherited an unwanted LG 49UH610V TV. It exhibits an alternating visual error: half the time the image shows more-or-less normally, with only 2–3 single-pixel lines showing near the top of the display, and the other half of the time the image is unusable, showing numerous single-pixel horizontal lines across the display which contain image data offset by ~30 pixels. The display alternates between the two modes every 63–64 frames in the video I took, suggesting it switches every ~2.13 seconds.

I have tried all of the following without success:

• Replacing only the T-con board with a salvaged unit from eBay. No change.
• Replacing only the main board with a salvaged unit from eBay. No change.
• Replacing both boards at the same time. No change.
• Replacing the power supply–main board cable with the one included with the replacement mainboard. No change.
• Replacing the main board–T-con board cable with the one included with the replacement mainboard. No change.
• Disconnecting each of the T-con–display ribbon cables one at a time. Even worse image or none at all – I can't remember.
• Covering various ranges of pins on the T-con–display ribbon cables with Kapton tape, as shown in two YouTube videos: A, B. Even worse image or none at all. ~2.1 second cycle did not go away.
• Trying a different power cable (C7/C8 connector). No change.
• Applying pressure while the TV is switched on to the long thin PCB at the base of the display that the two ribbon cables from the T-con board connect to. No change.

Based on the fact that I observe no change at all when swapping the T-con board, main board, and two cables mentioned earlier, these components must all working as intended. As far as I can tell, this leaves only the power supply board, the long thin PCB at the base of the display (like in this image), and the panel itself. I haven't taken apart the TV enough to confirm, but I believe the long thin PCB is soldered or otherwise bonded to the panel and therefore cannot be easily replaced. (On a side note, is there a name for this PCB)?

Does my conclusion sound accurate? Do you think this TV can be salvaged without buying a replacement panel?

Images and video are included below.