Thanks for these ideas!!
I'm using these:
https://www.crutchfield.com/p_703CINN2M/AudioQuest-Cinnamon-2-meters-6-6-feet.html. They are 18gbps, ethernet enabled and the longest cable running is 6ft. I've also tried switching them around and tried different inputs on the Marantz, but it didn't make a difference.
I recall reading the eARC connection(using the appropriate cables) would eliminate handshake issues. I could try picking up some 48gbps, ethernet cables to see if it will improve, however, I thought it should run fine with the cables I have when not passing 8k content?
Would replacing these with something like
https://www.monoprice.com/product?p_id=31230 make a difference for 4k content?
When watching ATV 4K content I saw no handshake issues with sr5010 paired with the LG C1 or the Viewsonic UHD monitor. The sr7015 shows no issue with the Viewsonic UHD monitor, but has trouble with the LG C1. From what I can gather the, cables, content, and components should work fine in both scenarios.