Volume Normalization - volume gradually decreases


I have a problem with Volume Normalization while playing FLAC files (I don’t know if this happens with other file types). Problem is the same with various albums.

Let’s say I have 2 albums in FLAC on playlist. Volume Normalization turned on. Louder album flacs are played normally, but the quiter ones (from the other album) at first are being played in the same volume as louder ones. And then, in about 5-20 seconds volume gradually decreases to the level, like there was Volume Normalization “off”. I tried many options with DSD, mixer etc… Nothing works.

Please help.

Volumio version 3.378, Allo Boss 2, RPi4