AlanD

Rob, Yes, I tried a different HDMI cable. I have a similar setup (Roku Ultra / Tivo Edge -> Onkyo AVR -> LG TV on HDMI1) and I was able to see the problem with nothing but an antenna connected and tuned to a local OTA channel, so that pretty much eliminated everything but the TV. I was able to get it to go a few hours without a reboot, usually after a factory reset, but it would eventually go back to rebooting more often. I got the main board from Encompass, which was the company that LG referred me to for parts. Other companies sell the main board, but their price was OK and figured I had a better chance of getting a new factory board from them. The part number is EBT65053201 and it was $133 plus tax and shipping. I thought for sure that would fix it, since I noticed that if I was navigating the Setup menus, they would get slow and unresponsive, right before the TV would reboot. Good luck with your issue.

Just wanted to provide an update for anyone following this or with a similar issue. I replaced the main board and it did not fix the problem. As a matter of fact, it got worse. I thought about trying a power board, but decided I was done putting money into this set. I ordered a Sony OLED and the LG is going to the e-waste recycle center. Done with LG TVs.

Same issue for me with the same model. It may have started with webOS 6.00.05, but I am not sure. It was very infrequent when it first started and recently it has become much worse. I had it reboot 5 times within the span of 20 minutes a few nights ago, so I started trying some things, including upgrading the software to 6.00.20. The latest software did NOT fix the problem. I did a factory reset after the update, which was one of the suggestions I saw online for this issue, and that seemed to fix it initially. I went 3 or 4 hours without a reboot, but the next day it started again. I have a similar setup. Not using the terrible webOS apps, just using it as a display with my inputs coming through an AV receiver to HDMI 1. A new thing I have noticed, when trying to update the software and changing some settings to see if they helped, is that the Settings menus are slow and become unresponsive, right before it reboots. I read on one of the forums that this is a main board failure, but I am not convinced. I think it is a software issue, but I may decide to order a main board and replace it, as this issue is starting to make the TV unwatchable. Correction. I upgraded to 6.00.25, not 6.00.20. I also called LG support. They had my try some troubleshooting, but 5 minutes after we hung up, the TV rebooted again. Considering a Sony OLED, but might try replacing the main board first.