Thanks for your reply.
After investigating, the problem only arises when resuming with the built-in audio plug-in and setting the sound at 0dB. In that case, it seems impossible to play the music again with the built-in audio plug-in
When resuming with the audiohelper plug-in, everything seems to work just fine.
Here is a capx if you're interested. But I'll just use the audiohelper plug-in to resume from now on, so no urgent fix needed as far as I'm concerned.