Hi,
This is normal behavior as MMA reacts on Android event (Playback Device inaccessible[headphones disconnected]) when this happen can you please Use "..." -> About MediaMonkey -> Send Logs and write down log id here before you send it so that we can analyze and add exception to prevent behavior when you are casting and controller/audio device gets disconnected?

When casting to network player and headphones are removed from android dev, the music pauses.
Oneplus 3, android 8.0.0, oxygenOS 5.0.8