Moving further discussion to here, which seems to be the more appropriate conversation.
I came up with a workaround, which I hope will help figure out what’s going on. When I get the “loading slowly” error message, which happens sometimes both on Qobuz and on local files, all I need to do to get the Devialet playing again is to switch to another zone in my setup and play the album there for a few seconds. When I then switch back to the Devialet, the album plays without problem or error message. In my case, I just have to switch briefly to a Bluesound Node that I have and then back again, which has done the trick a couple of times now.