It seems that this HDMI problem is serious.
If you Google Onkyo HDMI board problems the page really lights up. Also they get a failing grade for customer service.
Worse there are serious design flaws in the current Onkyo range.
They get too hot.
It seems service is only a temporary solution and extensive DIY is required for a more permanent solution.
The basic problem stems it seems, from a very poorly thought out board layout leading to poor internal air circulation.
It seems you have to replace a bunch of 100 mfd electrolytic caps with larger ones rated to 105 degrees.
Other component changes may e required and installation of fans is apparently mandatory.
This is too much to expect from the average consumer, and Onkyo receivers need to be downgraded to junk category. They should not be recommended on these forums. In fact they should have an avoid designation.