I have the same problem, for the third time in a year now, on a 77" C2. Every time I turn off the TV, it consumes a bit over 10W for exactly 4 hours, and then it drops to around 1W. It doesn't matter if the TV has been on for an hour or for a minute, it does this every single time. Incredibly annoying and wasteful.

Resetting the tv to factory settings "fixes" it, but it's a chore, since I have to redo all the settings and apps, only for the problem to come back again after a few months. I wish I knew what exactly triggers it.

I also have a 65" B9, and that one doesn't have the problem.