And what happens when you try recording on each other’s equipment?
What he said.
You could try bypassing PulseAudio.
You could try bypassing the computer.

Now on sale at Sweetwater Audio.

That, pretty much as you see it is how I recorded my technically perfect ACX test submission. People have posted on the forum using Zooms H1 through H6. Granted you still have to buy the memory chip and batteries, but since it has nothing to do with the computer, the sound is perfect.
I believe you can leave the USB cable connected and not have to use the on-board batteries. You can also use it hot as a computer-connected microphone, but I wouldn’t do that at gunpoint.
I’m down for a 9 hours audiobook!
You can troubleshoot your machine while you’re recording your audiobook. If you find out what’s causing this, post back. Nobody has ever solved this.
Koz
The accessory package comes with a wall power supply.

Mine came with no memory chip and I contacted the company and complained loudly about that. “The recorder comes out of the box unusable!!” I know this unit used to come with the smallest-possible memory chip to get you going, but the later ones don’t. This wasn’t a big deal for me since I live in Los Angeles and I’m two miles from a store that stocks chips, and Sweetwater did offer to send a chip, but if you live in Middle-Of-Nowhere, this could be a problem.
I told them their advertising needed to be very clear about this.
Koz
From memory, one paper towel roll wasn’t high enough, so I used three bathroom rolls instead. You can wear your engineering hat for a minute. The rolls put the microphone at appropriate height, they’re acoustically dead and they don’t transfer vibration from the desk.
I also used oblique positioning (B), not straight-on.

That helped with the signal to noise and greatly reduces P-Popping.
The recorder produces stereo—two channel—and I mixed it down to mono for submission. That adds the voice volumes and reduces random background noise as the square-root of the doobly-do.
A separate recorder also gave me an automatic hardware backup for the performance.
Koz