Just wanted to thank everyone who shared their solutions here. My 65UJ6200 TV was also in pretty bad shape. Youtube and amazon prime video would freeze the picture but the audio would keep playing. And then after a second the picture would speed up to catch up to the audio. I kept getting LAN disconnect and reconnect messages. My wifi also didn't show any networks and sometimes just crashed.
I took apart the TV just removing 19 philips screws. I then gently unplugged the ribbon cables, some of which were a little stuck, and gave them a wipe with rubbing alcohol. My wifi connector wasn't a ribbon cable when it connected to the wifi module, so I just unplugged and replugged that connector a few times. I also didn't mess with the 90 degree bend, since it seemed normal.
Everything is fixed! If you're having this issue, seriously try taking it apart and cleaning the ribbon cables. I wouldn't be surprised if just disconnecting and reconnecting them would fix it.
