^ good for you, sir.. congratz, no issue with your 343
would you not mind sharing why did you attempt to reset it? was it after a FW upgrade?
In the manual it says to press the power button WHILE holding down the power button on the unit itself. Display will say "Clear" and reset it to factory settings.
Last night, I had the same issue again (around 10pm). This time I knew what to do. I removed everything and Unplugged it overnight for the AMP DIAG to clear from the receiver's memory.
In the morning, I did a more methodical install starting with just the Front Speakers, play some content for 15 minutes, then added the center speaker and repeated the cycle adding a speaker every 15 minutes (powering down every cycle before adding a speaker).
This time I left out the powered subwoofer. Lo and behold 4 hours later still no issue.
I remember some years ago I had a problem with the active sub (blew a fuse) so I opened up the subwoofer. Lo and behold I saw the culprit, some damage on the circuit board (blown transistors). Now I think I appreciate the amp protect features of this product which I did not have on my previous Denon (purchased last 2010). It was probably the active sub that caused damage to my prior receiver. I DID have the amp repaired before I sold it so I'm not a scammer he he he.
From the service center, they said this model is a "entry level" so it does not have a firmware update.