My problem persisted so I ended up going through Samsung support to see if they could resolve it.
This was done via chat on the Samsung website. These front line support people asked me to try some basic debugging procedures, including doing a factory reset. Long story short, these didn't resolve it so a warranty claim was initiated by the final support person and the local warrant service provider for my area came to my house and replaced the "motherboard", which has resolved the problem.
Overall I got the result I wanted and I'm glad they came to the house, but the whole process was a bit painful - three consecutive days chatting with different Samsung support people before the warranty claim was started and then had to wait for the motherboard to be available - luckily this was only a week but they said it could be up to 3 weeks.
For me going through the warranty repair process is better than having to repack this large TV and return it and then buy a replacement - you'll have to decide what is best for you.
Because my problem was intermittent the chat support went over several days in order to confirm that their recommendations didn't work. This involved using the settings menus so nothing that a tech savvy person couldn't do in their own.
If you follow my path make sure you keep track of/document the debugging steps you have already tried yourself - you might be able to shorten the chat process. You can send them short (10 second or so) videos and JPGs through the chat to show what you have tried to avoid having to repeat them with the support people.
Don't delete this documentation until the fix has been completed - because my problem was intermittent I had to go through this again with the service people before they went ahead with the motherboard replacement.
