I can only go with my own experience owning a Denon 4308CI and a 3312CI and both have defective HDMI boards. Still after 2 weeks can't even get the part from Denon.
The authorized repair shop tells me that the HDMI cards are on back-order and in great demand. Hence, a lot of people are having the same issue.
So far with only two Denon receivers in well vented installs w/cooling fans I have a 100% fail rate on their HDMI cards. Most people do not have cooling fans so I know it's not heat.
Both receivers use different, speakers, BR Players and TV's.
This to me is a very high fail rate. The Denon 4308 and Denon 3312 are supposed to be different classes of quality in the Denon Receiver lineup yet they both have HDMI cards that failed???
I would like to see both cards and compare them as well as the dates / ver numbers and factory they came from. There could more in common with the cards or the voltage. An HDMI card can put out 8 volts, that might not seem like a lot but if the board had one bad connection it's only a matter of time beore it's fried.
I was going to get the new high end Denon for my main video room but I need to know about these HDMI boards first. If they are the same I might go for the top of the line Yamaha.