Problem with track sorting in Spotify Premium

[blackmorpheus]

I have an iMac with iOs system. Recently I turned to Spotify Premium, but the tracks are not played in order! After the track I select, Spotify choose a random track from my playlist, even if the shuffle mode is off! The same thing happens even with the albums. This concerns only the app. If I try by the web player, the tracks are played in order, but I can't sort them because the sorting tool is not enabled! 

Can someone help me, please?