I have quickly tried to look at the cause of music playback stopping for a short while when pressing the power button. It seems that this issue does not occur with e.g., the stock media player (or mediabox). However it seems to occur with e.g., QSpot and SomePlayer. One possible reason could be that the stock media player utilizes Mafw for playback (while e.g., QSpot uses pulseaudio directly). Anyway, this was just a short note; some more investigation is still needed.