Zoom H4n USB microphone - wrong pitch

Hello community!

As all schooling activities have been going online since october, me and my students are constantly striving to improve the video conferencing quality (music lessons).

Most of us own a Zoom handy recorder (H4n, Q8 or H1), which is a very capable device and serves as USB microphone - it's just that most of the time the pitch is wrong up to a major second in either direction, which makes listening impossible despite the sheer audio quality being better.

The problem seems to be common to all Mac and PCs and all Zoom devices, it even happened once that my pitch was altered while using the built-in-mic and only the other party the Zoom H1!

I'm sure there is a simple explanation, but two weeks worth of googling were no help at all.

Thanks in advance for your answers :)