Bad static type noise interference on Audacity podcast recor

I made a recording of a conference using USB stick in QU-Drive on our church A&H Qu-24 digital desk.

And in some sections during the session there appears very bad static type interference, like radio interference.
For all of the sessions the speaker was using a Sennheiser handheld radio mic and there was none of this noise coming through the PA, everything sounded good. It was just when I loaded the wav file into Audacity I noticed this noise in one or two sections.
In Audacity I went through the normal Noise Removal process of selecting a Noise Profile sample of a section where this static noise occurs on its own and then selecting the whole section where noise interferes with speaking and selecting Noise Removal. It reduced the static a little bit but you can still hear it. If I reduce the noise by too much it sounds metallic and broken up.
Any ideas how to eliminate/reduce this static and how this appeared in the first place, it has never happened before and it only occurred in some sections.

To remove static you need the DeClicker plugin here , ( get the DeEsser while you’re there ).