Actually, I was listening to the headphones, but the distortion is very light and I, for whatever reason, didn’t catch it during the shoot. I believe the cause of it was that the mic had been used for a live production prior and the output from it had been set to +12 dB, where we usually keep it at +0 dB for video shoots.
I didn’t catch this until after the shoot. And, yes, the mic was going straight into the camera.
Thanks for the help guys, I’ll try the suggestions you’ve given me.