Popping sounds when playing multichannel

I hear popping sounds when I play multichannel, regardless if Roon upmixes or if the original is multichannel.

The situation:
Roon Optimized Core Kit

  • audio device set up as:
    –max sample rate (PCM): 192 kHz
    – max bits per sample: 32
    – channel layout: 5.1
    – send stereo/mono content as 5.1: yes
    – multichannel mixing: downmixing as needed.

HDMI cable
Denon AVR4520 receiver

Track: Birdsong
Artist: Ludovico Einaudi
Album Seven days walking
Source: Qobuz Flac 96 kHZ 24 bit

Signal path:
Channel mapping 2.0 → 5.1
Roon Optimized Core Kit
HDDA Intel PCH HDMI 0 (Alsa)

The Denon receiver
acknowledges receipt of 96 kHz 3/2/.1 format and remaps to 4.1

Same when changing settings
channel layout: 7.1
send stereo/mono content as 7.1: yes
and channel mapping in Roon signal path to 7.1
Dowmix as needed

When "send stereo/mono content as 5.1the popping sound is gone.

also popping noises when in settings:
channel layout 5.1
multichannel mixing: downmix as needed

Denon AVR4520 acknowledge receipt of 96 kHx 3/2/.1. (thus 5.1)
Denon down mixes to 4.1.

Track: Concerto Fantastico: 1. Allegro Affetuoso (La
Artist: Annar Follesø
Played from NAS, download from label 2L)

When I change the setting channel layout during this track to 2.0
The AVR confirms receipt of 96 kHz 2.0
and it umpires to 4.1.
There is no popping.

Anyone knows how to solve this?