Potential failure with volume controle

Hi, please I would like your advise about a failure during PCM Network playing :

Condition : Audiomat Tempo 2.9 Network / Audirvana S / PCM without up-sampling or other.

Trigger: When puching the “+” volume button, the value changed to 20db, then dicreasing constantly.

Tests : Mac / Windows, firmware change, all equiment rebooted properly.

Final : Network PCM player fonction not working anymore. Same on DS audio, native OSX, etc…

Do you have any feedabck about this kind of issue? Thank you.