I've seen mention of the Netflix "black hole", but not of the perpetual reboot loop that I experienced when setting up FiOS STB on my new UN85HU8550. This one almost caused me to return as a Lemon until I figured it out.
Seems that if you try to display the Guide data for the FiOS STB before the TV has had sufficient time to download all of the guide data, the TV will drop into the perpetual black hole of reboots. FiOS in my area delivers more than 1000 channels, which apparently takes some time to dowload.
To get out of this particular reboot is tricky: after the SMART boot screen, you'll have about 5 seconds where you can enter the Service Mode code and move the cursor. But first, you have to get the TV to turn OFF...by hitting the Power button repeatedly right after you see the smart screen.
IIRC, the sequence to do a factory reset is:
<Service Code> (Google it, it is 4 buttons plus Power)
If you can get that done within a couple of seconds (not that hard, if you're ready), you will be greeted by the New TV Setup screen the next time you power on the TV. You will of course have to totally reset everything to your liking.
I went through this far too many times before I figured out what was causing it. Once I did, I made it a point not to display the Guide (in any form) for 12 hours (just to be safe). Since that, the guide works fine and I haven't wound up in a black hole since.
I have no idea if this occurs on any other version/model. And if everybody already knew about this one, sorry to bother you with my experience.