Logic Pro changes the tempo of my songs

I've imported multitrack files of my band's live set from a USB into Logic with no problem. My usual practice is to copy individual songs from this large file and paste them into another Logic file to work on individually. I've done this in the past with no problems. All of a sudden, Logic is changing the tempo of these songs when I copy and paste them. I'm guessing it's something to do with the new Smart tempo control - I've got everything on "Keep tempo" but it doesn't keep the tempo.......would be grateful for any thoughts.