I had nothing but persistent problems with my setup: sources - Radiance - HD621 - G68. I tried everything - switched Radiance and HD621, multiple FW updates, different brands of HDMI cables, different lengths of cables, tweaking audio EDID settings - all to no avail.

And I was crazy enough to do this with an XD several years ago and more recently with a 2021. Same thing all over again. I had multiple conversations with the excellent folks at Lumagen - they basically told me Meridian's horrible implementation of HDMI, and their off the shelf made in China HDMI board are the culprits. They offered to take my HD621 and bench test it, but by then I had had enough, threw in the towel and got rid of the Radiance.

And I couldn't be happier without it - my system works reliably with no more constant relays clicking, blank screens, and absent audio. If I move to a non Meridian processor I would consider a radiance again.