I heard it right near the end as the only other point where it was evident. It's really impossible to tell which part of the signal chain this is coming from: guitar--->effects loop perhaps-->amp
or
mic-->direct box perhaps-->zoomR16

I'm afraid without being on-site to diagnose and debug, I won't be of much help. It certainly doesn't appear or sound to be overdriving of the mic, nor clipping of the input stage on the Zoom unit. This sounds like a static build-up/release issue to me.

-Scott

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