IDENTICAL setup and problems. I'll also add this: with the Roku connected to the Phillips Sync, I think the Roku likes to send the Sync HDMI-CEC commands because the Sync may occasionally switch inputs to the Roku.
Through a bunch of trial and error I have discovered that the issue boils down to Dolby Vision compatibility. If I set my display type to 4k HDR10. I no longer have these issues. Using Auto Detect on the Roku would periodically upgrade or downgrade what my TV was capable of doing this making the problem intermittent as apparently I did not watch a lot of Dolby Vision content and the issue was not always apparent.
