Devialet has determined that when using bluetooth, a small percentage of Phantoms may become silent after hours of playback (no matter which app is used).
This is a known issue for our latest firmware (2.11.3 and later) due to the bluetooth memory management. It can be temporary solved by resetting your Phantom or rebooting it.
Our software team has been aware of it and making sure the issue will be fixed in our next released, which is expected to be released in middle of February, 2021.
Meanwhile, the workaround would be using other sources before the official release for the next update.
Devialet Customer Service and Support