I just checked again, and you are right, it did not apply the settings, so the bug is still there.just to be clear: the sound actually got louder when setting maxvolume from 10% to 20% after the restart? Because for me the webinterface remembers the set value, but just does not apply it so it is in fact at 100% while the webinterface still shows 10%.
The video sounds like a really small fan running at low speed. It is hard to judge how loud it is from the video.
When I put my ear to my Amp I notice also it makes a very faint noise. I never noticed that before. Just when turning the Amp on with the remote it sounds like a fan that starting up. You hear the frequency increase. Not sure you should expect something like that from a SMPS. I usually only notice the fan when the Amp it hot, but then it speeds up for 1 sec every 3 seconds. it could be they changed the fan’s response to temperature to make it less noticeable.