And I have already noticed some small bug with the latest foobar2000 mobile version. Here is my situation description:
Started a playback. Then left the phone untouched for a while. Then wanted to increase the volume, pressed the lock-button to light the screen up, and pressed volume-up hard button. Indication showed increasing the multimedia-volume from 10 to 30 (max) points but actual volume didn't change. Tried to adjust the sound volume a couple of times both directions, then slided my finger up to bring the desktop on the screen. Then tried to adjust the sound volume again, and it worked well. Locked the screen, tried again - works well.
From that time I didn't try to reproduce the situation.