Playlist keeps changing

Hi all, I have a playlist I have created on my iTunes file and Sync'd with my iPhone 6 Plus. It has been fine and music is always in the same order ( I can almost recite the next song on the list all the time ), Today I get an e mail my iTunes match has been renewed and then all of a sudden the Playlist I had created (and used with no problem for months ) has lost some songs and has jumbled its order, both on iMac and Phone ? I have not done anything different than usual, and am wondering why this has happened ?