this also just happened to me over the past few weeks with my MU8000. i wonder if it's a bad update?
i will try the october update when i get home. the banding has gotten severe and the set now looks worse than my $275 TCL 4K i just bought from costco. it's really annoying to even look at or watch the tv anymore. I hope samsung does right by me.
Unfortunately they were unable to fix my mu8000 after replacing the panel and power supply. I opted for a store credit and bought a sony xbr75x900f.. incredible picture, no vertical bandung lines. So sad, been a Samsung buyer for years.
After the new panel failed they contacted me with the store credit offer...I had to make several calls to reach the team who initially called me and left the message but after that it was painless.. bought my tv through Magnolia with Best Buy, they were awesome with the exchange, setting up the new tv and taking the old one.