Music pauses when iphone goes to stand by or lock screen

[Moeasr]

Hello! 
I have an iphone 6 plus with lates IOS 8,1 and sometimes when i leave my phone spotify pause the music when phone goes to stand by or when lock screen comes! I have to remove the app from the background and run it again then it works again! 
tried to uninstal and instal and did not help! it happens on my Ipad too! must be something wrong with new app! 

Cheers 

Moe