Roku Ultra + ARC Soundbar + 4K UHD TV = screen blanking out
So I recently upgraded to a new Samsung 4K UHD TV (model# UN65TU7000). Everything worked fine for the first week, but a few days ago I upgraded my HDMI cables to 4K UHD 18Gbps lines. Ever since I did this, when watching content on my Plex Media Server, the screen blanks out to black every 3-5 minutes for no apparent reason. I've tried swapping out the HDMI cables, including going back to the one I'd previous used that had no adverse issues. I've tried switching the display type to Auto, 1080, 4K 30, 3K 60...nothing. Changing the tv display from standard to dynamic, to natural...again nothing. I'm coming up with a loss of what else to try, but nothing seems to help. As I said, it all worked for the first week when I set it up, the only change being my switching the audio from Digital in/out to the HDMI Arc (on the soundbar) and upgrading to newer 4K capable channels. The only other thing I can think of is that the soundbar is only HDCP 1.4 compatible, but again, this only seems to affect my watching Plex from my local server, not Netflix or any other streaming services I watch via Roku.
Here's my setup and how it's connected;
Ethernet in to Roku Ultra player
4K HDMI out to Samsung HW-R550 Soundbar
4K HDMI out to Samsung UN65TU7000 TV (HDMI port 2 for ARC compatibility)
The only other thing I can think to do at this point is to disconnect everything, reset all components to the factory defaults, and start over from the beginning (with no guarantee that will solve anything.)
If someone can offer an idea of what other settings I could check, change, etc on any of the components, please let me know.