Why does the Play Music lock screen widget keep closing when I press pause?

[David Samuels3]

I have a Nexus 5 and Lollipop. When I play music from Play music and hit the pause button on my wired headphones, at least once out of 4 times, the widget will disappear from my lock screen. This causes me to have to unlock my phone and go into Play Music to resume playing music (if I hit the play button on my headphones nothing happens). I've had this problem with various headphones