I listened to your sound sample and it definitely sounds like clipping. My first thought would be that the camera input is being overloaded by the receiver. I work with a C100, and in fact, I did that today. Sounds like you are using mic in, if so, there are trim adjustments in the menu to help prevent overloading the pre-amp. Was your assistant monitoring the audio with headphones during recording? If overloading the input is not the problem, then maybe the wireless system has issues. Good luck.
P.S. one time when we were recording with the C100 t went haywire. No matter what we did, the audio into the camera was distorted. We powered down and removed the battery for a minute and the rebooted. It worked fine after that. Must have been a ghost in the machine…
Bob