Importing tracks

Iv had this issue in the past quite a bit. When importing instruments or vocals they seem to slow down or speed up relative to the original. Iv check and made sure their bit rates and such are all matching. Iv tried just about everything I can think of. I have some rappers with tracked out beats that just won't import at the right timing. Iv tried converting them myself and about everything else I can think of and even had re-exports of the instruments from the original DAW they were made in, in different bit rates and file types and such.