This issue turned out to affect any casting device, not just Chromecast. The fix was an update to Google Play SERVICES. Latest version being 11.9.75. It was finally pushed to me last night. I am amazed at the difference it's made!!! All this time I've been blaming my crappy satellite ISP and it's been a bug in GPS. No more GHs talking over each other, no more "sorry, there was a glitch" or "sorry, something went wrong". The GH I'm speaking to answers and not one 30 feet away! Replies come in 2-3 seconds instead of 10 and even GPM is working like it should.