Cover arts are't showed up with ape files

Hi there, I installed volumio 2 in Ras pi 3 connected to KEF Egg, and it performed awesome .
But, I have some issue cannot be solved.

Most of my music file are compressed to ape file, however, these cover arts cannot be seen in Browse page, but can be showed in Playback page.
Flac and mp3 files work well. Is this a bug needs to be fixed ? or my setting go something wrong ?

Another problem is, I can’t control volume when linked to KEF Egg(DAC mode) by usb ,should I change some setting ?


Browse page

Well, I’ve exactly the same problem with album art.

All my files are encoded in ogg, and there is a cover.jpg in every folder. The album list doesn’t show any images:

But if I click on a certain album, it is shown:

Is there a recommendation on the size of the files?

I programmed a bit against the API and indeed, the album list gets the wrong album art URI:

artist: Paganini, Nicolò
albumart: /albumart?icon=fa-dot-circle-o
service : mpd
type : folder
title: 24 Capricci
uri: albums://24%20Capricci