Any 4K content that I try to play via YouTube is dropping frames badly.  What makes it worse is that there are no options to force that content to play at a maximum resolution of 1080p.  I can only assume that this is a YouTube app issue as when I purchased the TV last year 4K content played without issue.

I was wondering if anyone else has this issue, if they have solved it and what you did to stop this happening.

My TV is a KD-55X8577 which is connected to the internet via an Ethernet cable.