[WP 8.1] Switching "Availible Offline" off for no reason

[Idekar]

Sometimes a playlist stops playing in the middle and when i unlock my phone to check why this happened i notice that the "Availible offline" option is turned off  for this playlist. Sadly it happens very often and is very annoing because i can restore my playlists only when i am able to connect to Wifi(and its not so easy to find because i mostly listen to music in public transport). I always make sure that my phone is locked before i put it into my pocket  so i guess it's not because of missclicks. Before switching to WP i used Android version of Spotify and such a thing never happened so i think it's a WP issue. I wonder if anyone else experienced this issue and if there is a way to prevent this from happening. Thanks in advance for any help.

[Edit]  I am using Nokia Lumia 635