TV screen damage after disassembly?

I was given an LG 50UH5530 for free that had a backlight problem. I replaced the backlight strips ok, but now the picture on the right half of the screen isn't displaying greys correctly. Pure white shows up with slight red tint, black and even colors seem ok, but any mid-grey tones just show up as black. I swapped the ribbon cables to the driver boards and the problem stayed on the same side. Did I ruin the display while I was poking around in there, or is there additional troubleshooting I can do for this?

^ Pure black/white ok, but greyscale all messed up

^ meant to be pure grey screen