Hi,
Well initially I though that my issue was solved but it's back. Here's some more details.
The issue is only with iTunes on desktop. (Mojave 10.14.4) whenever I listen to music and I pause and come back only one Homepod will play music, I have to manually go on iTunes in the Airplay menu and un-select and select my Homepod (pair) and most of the time the music starts to play in both of them but not all the time and in that case I have to quit iTunes and launch it again to get stereo mode back.
I tried everything possible, restoring both my Homepods, removing them from the Home app, restoring macOS but the issue is still present. One thing i'm not sure about and maybe it could be an issue but I use a VPN service on desktop (PIA) but i didn't have that issue prior the 10.14.4 update so i'm not sure it could be related.
Also This issue is not present when streaming directly from Homepod, iPhone or iPad.
Any suggestions would be greatly appreciated.