Dropped audio frames/wrong audio with the MRC1

I am using the FX1000 with the MRC1. While recording dancing at the wedding, the last clip on the card the audio dropped out 3 times for about 40 frames (each time the duration was different & there was no dropped video frames). The last time it dropped frames the audio it recorded was from 5 minutes earlier on the same clip. Usually I also record to tape but there were only a couple of dances left so not tape backup. I tried to re-import the clip & no difference. Any ideas why this happened?

Thanks in advance for your help.

Allen