The phenomenon in question seems to be well within the domain of casual recording, given the example at the top of page 2. I am not personally real sure it's going to help a lot, though. At this point in the game, the only way forward is to return the accordion for the purchase price, right? Or possibly in exchange for another model with normal bass range. The manufacturer has fairly convincingly demonstrated that there is no solution forthcoming for the problem with their extended low bass reeds. Documentation of the existence of superior accordions might help this case, but anyone can listen to the sound of that first clip and understand that it would not be acceptable. Of course that's irrelevant now, the same recording would have to be done with the new bass reeds, but assuming it's still reasonably conspicuous, it should be sufficient. If it isn't so conspicuous, then you have the recording technology problem described above. Anyway, much depends on how far the manufacturer is disposed to go, to make it right.
I listened again to the clip on page 2, and was again struck by how awful the treble sounded. I said something about that at the time - the bass chatter strikes me as a match to the beat frequency between the musette tuned reeds. But aside from the bass chatter problem, is that musette tuning good for something? I have a fairly high tolerance for musette tuning, and old used French accordions with some tuning issues, but the sound in that clip would drive me to the nearest accordion tuner. And here it is, pretty clearly involved in this bass problem. Wouldn't it be great to find out that tuning up the treble to a less rowdy musette actually fixes the bass problem, even with the more powerful original bass reeds?