spotify is unresponsive

[12148689661]

so i have been on spotify premium for a year now and have just bought a new sd card which is claas 10 for my phone and now once i sync my playlist it starts to run increadibly slow even if it is using songs that aren't downloaded. 

i think this is to do with the way the music is been stored offline because it will run completely fine till i sync the playlists onto the sd card. i also took the sd card out and sync it onto the device storage and it worked fine.

i have reformatted the sd card tryed reinstalling 3 times with same problem and my sd card records high quality videos so i know its not the speed thats the problem.