Yes, it is relatively common. It is intermittent LOOSE CONTACT INSIDE THE SPEAKER BINDING POSTs. It is a real issue that Marantz should address.
If you live or bought your unit in Australia, you can claim a full refund under consumer guarantee laws, that products or their parts should be fit for their purpose. This model has faulty speaker binding posts.
See post 3486.
There are real issues with the speaker binding posts - mechanically, and perhaps metallurgically.
The mechanical construction of each binding post is unsound
. The electrical components of each binding post is made up of three metal parts:
1. metal A that is soldered to the output trace on the circuit board,
2. metal B that forms the female part of the binding post. This, metal B is simply in contact to but NOT SOLDERED to metal A
. This flimsy contact would definitely fail over time - because the contact is due only to pressure by the plastic casing. Plastic casings, in my experience, harden and lose flexibility over time.
3. Metal C that forms the male part of the binding post.
Metal A and metal B are not soldered together. They are even made of different materials. I am not educated in chemistry but I am thinkng about galvanic corrosion. Even if the contact between A and B are now good, over time, with galvanic corrosion ...
I opened up my unit, pulled out all the binding posts, then reconstructed them - soldered together the appropriate metal parts (metal A and metal B) of each. With that, I no longer suffer the annoyance of loose-contacts every couple of days or so.
But not everyone can safely do that.