Problem with pops (parasite sounds) with .mov imported media into FCP 10.2.1

Why is the audio from my .mov media showing multiple pops and clicks. I can see it in the waveforms, but the original .mov files are clean. I have .mp4 files imported into the same event. This problem is new, since updating to Yosemite.

Please advise. Should I convert the .mov files to .mp4?

Thanks.

Christine