Allo Kali - first hand experiences

Hi, just received the bundle kali+piano 2.1.

Items were well organised within the package. Just a bit surprised that the units are not coming with any user’s manual.
True that you can find some material on Allo’s website, but some more detail would have saved some time.
For instance, since the issue with 24 bits and white noise is well known, why not including a note recommending the resampling to 32 in Volumio?

After assembling the electronics and firing the power up, I have setup Volumio for the Piano2.1 in dual stereo. Ok, easy.

After forcing the resampling to 32 bit, as said above, the combo kali+piano works nicely, except I can hear a distinct audio glitch when I skip different tracks or switch sources. Quite annoying.
This is not related to sample rate frequency, it occurs even within same album. The blue LEDs of the Kali switch off for a fraction of a second then back on, and this is when the glitch ( similar to the noise you hear when switching on an amplifier) is audible through the loudspeakers. I have already tried to force resampling (192K) with no luck.
This is definitely related to Kali since the Piano connected straight to the RasPi does not exhibit same problem.

Has anyone experienced the same? Possible solutions?

Last but not least: when looking at playback setup in Volumio, I have noticed that the hardware mixer offers a number of different possibilities.
Has anyone a clue of the difference between different settings (see pictures below). I have just noticed that some allows for direct volume control, others not (so maybe more suitable for bit perfect playback).
I have not found any useful info on Allo site on this respect.

Thank you in advance for your suggestions.