I'm currently using Studio One 3 Professional. For whatever reason, I've been having issues with imported tracks lately. A friend of mine will record guitar at a specific BPM. It's on time with the metronome when it's exported. But when I import the track and put it on grid, it starts to go off beat. It's as if it's slightly faster that the original tempo. So by the time it reaches the end of the song, it's half a beat off.
I'm also having this issue with drums I recently recorded. I had an extra mic set up on a different computer. When I import that track and line it up with my other two drum tracks (that were recorded at the same time), they start to sound off by the end of the song even though they were perfectly aligned at the beginning.
Any advice would be appreciated!