Spotify doesn't continue playing after exiting Siri

[jezza1685]

When I'm playing music on Spotify, I activate Siri by holding down the home button, Spotify stops as it should, but when I exit Siri it doesn't always continue playing as it should. Some of the time it will continue as expected, but not always.
I'm using Spotify 4.1.0.941 on iOS 9.0.2.