Bluetooth audio volume problem

[Topataco]

Ok, so I have a 1020 which I regularly use to stream music to my speakers using a Bluetooth dongle thing and mytube, and recently the volume refuses to go above 13. I've tried raising the volume on both the music app and mytube, but it won't let me, and I've tried looking for a setting in the obvious places, but no luck either. Any ideas about what may be the problem?