Problems with wifi/ mobile data

[carmentxx]

When I have full four bars of Wi-Fi, or 4G mobile data all other Internet apps work absolutely fine on my Samsung S6. However with my Spotify Free acount I'll press shuffle play and automatically lock my phone but despite my data or Wi-Fi still being on and used the music will play for a few seconds and then stop. On the app the music titles fade as if there is no connection but will go back to white once I go back onto the app, effectively reloading it all when it should be loading while I'm off the app anyway. Please help!