I'm sorry to hear you're having issues. I've been down this same road with this receiver, I feel your pain.
I know this may sound like a silly question, and I don't mean to insult your intelligence, but are the new HDMI cables connected in the correct direction? They are active, so will only work in one direction. Lastly, my first RZ50 would lose OSD also. I didn't lose audio, just black screens and massive handshake issues. I was fortunate enough to be under the exchange policy of where I purchased the RZ50 and received a new unit.
You could try using one of the included HDMI/USB power adapters that came with the RUIPRO HDMI on the Cable Matters HDMI. You shouldn't need them on the shorter RUIPRO cables.
Lastly, try changing the HDMI OUT to Main + Sub. (Shortcut button located on the remote at the top, in between Power and Sleep) My first receiver would work if I did that.