Final Cut Pro audio sync problems

I am importing VHS tapes using iMovie after the import finishes I export the project from iMovie as a Final Cut Pro XML file for editing in Final Cut. Most of the videos i've imported are usually fine but there have been a few where the audio is way off. it is using dv audio, i've read that it could be the sample rate. This last project I exported as an XML and brought into final cut I noticed in the final cut timeline the audio track is longer than the video track how is that?? very strange. If anyone could help me out I would greatly appreciate it!