drum machine track not syncing with live recording - Final Cut Pro 7

Hello, I have a real conundrum, and will be very impressed if someone can help. I am producing a live performance video for a band that uses drum machines. I would love to add the drum machines to the audio track to bring them out more/improve overall sound quality. However, despite making sure all the audio tracks are 48khz/16-bit, the drum machine track does not sync up with the rest. It might even be drifting in and out. I can't really see a way out of this. The drum machines the band use live are midi powered - could this be where the problem lies?

I used a Zoom H4n as an ambient mic mixed with a mono feed from the sound desk, and I'm editing with Final Cut Pro 7.0. The audio tracks from the Zoom sync perfectly with the camera sound. Any suggestions would be gratefully received!

Thanks Rafael. I have checked and all the sequence presets are correct. It is not the Zoom files that is the problem as they sync fine with the camera audio, it is just the MIDI drum track I am trying to add.