At last, my problem is solved!
The short version
Updating the Denon 2310's firmware from 69 / 30 / 14 to 69 / 34 / 15 did the trick.
Thanks a lot to all of you!
The details
It took an awful long time because of Denon France.
The site says there is no warranty if the hardware was not bought in France-- they don't care, and I've had proof of it.
I tried getting in touch with them nonetheless, because a few members here had had a great experience with Denon UK (getting the firmware update immediately, even though the warranty was six months void in one case, and with Denon paying for the shipping in another); so had I : when I called them, the person I had discussed the problem with me (as I reported here): they were aware of the issue, that updating the firmware seemed to solve the problem according to customer feedback, that they were investigating it and informing Denon Japan; indeed, I remember Denon UK had asked a fellow member if he could send his Star Wars set along with the player.
In other words, Denon UK cared about its products and its customers and tried to solve the issue and to understand it.
It took me two weeks to reach the person supposedly in charge at Denon France. I had been told to call him, and had tried several times; they eventually told me he was at some expo.
I still could not reach him when he was supposed to be back.
Eventually, I did, and he told me he was not a technician at all, that he kept getting customers and answered sometimes.
Then he told me there was no way Denon France would update by firmware because I had bought the A/V receiver in another country; I explained I thought that maybe they could make an exception because: Denon UK had been extra nice with its customers (as stated above); it was not a matter of understanding what was wrong with the unit, nor repairing a burnt device, but merely updating the firmware; I thought they would like to investigate this mysterious issue.
Nothing doing.
The tech shops they farm out al the servicing told me to try and ask someone in charge of customer service or commercial deals.
I did. The guy replied he was not a technician and did not care and I should ask the tech guy; he would not listen to anything, especially the part where it was precisely he who was supposed to make a decision.
Two whole weeks lost because of a bunch of idiots who did not care.
Granted, they state it clearly that they won't touch anything bought outside of France, but still, I expected some professionalism from them: professional interest in an issue reported to them for the first time, politeness and courtesy.
I could not deal with it until yesterday; I went to the tech shop yesterday afternoon, gave them the receiver, and got it back this afternoon (they called when they opened in the morning, but I couldn't go).
I re-wired the whole thing, checked the exact version of the new firmware, did not bother reconfiguring all the parameters, just made a quite speaker test (the chance of an error was nil, but I still did it), and tried
Episode IV.
I only had time to check four of the drop-out I had spotted, but it worked fine in all cases. I'll check all the other spots on this and the other movie (Episode II), but the issue has obviously been fixed by the update.
It cost me more than a cable, but I'm so unlucky I didn't want to take any risks. Besides, by ordering the amp, the speakers and their stands from Richer Sounds, even with DHL shipping, I had saved the equivalent of the amp's price in France (!) (and I got the next version of the speakers, too!), so I could "afford" paying for the upgrade.
Also, because two clerks at my bank made terrible mistakes (professional and behavioral), the manager refunded me some money (nearly twice as much as the upgrade cost me), so in the end I can consider I didn't pay anything for the upgrade.
As soon as I can, I will watch
Episode IV again (it works better as a stand-alone than
Episode II).
I had been waiting for years to get
Star Wars in digital form; I expected there to be a special 30th Aniversary box set and had been disappointed by the lack of it. I had not seen the new movies since their theatrical release, Episode IV since the 2007 edition, and Episodes IV & V since even longer (I could not go see the 20th Anniversary editions).
Having the movie marred by those drop-outs was thus a terrible let down-- there
are much more terrible things in life, of course (I've had more than my share of terrible); relatively speaking, though, it was awful, after so many years of patience and longing.
Thank again!
I'll keep visiting the site.
All the best,