I'm having the same exact issue. And it's only recently. I'm rooted and running cm 12.1. This only started happening in the last week or so for me. Tried downgrading to older fbreader but that didn't change anything of course.
Wait so if I want to access media in my car I have to press Media? That's crazy complex! Never occurred to me.
I'm reminded of Microsoft Help where the first step is always "Is the device powered on?"