sound is gone after 3 hours of zoom

[ohad]

Hi

I use a video camera connected to a video capture card connected to usb port on a laptop.

Recently, in long zoom sessions, after about 3 hours,  the audio in is gone for a few minutes and my students can not hear me.

I tried to switch to the laptops mic and it works sometimes, and sometimes there is no audio in zoom also from the internal mic.

after few minutes I get the audio again but I have these problems repeatedly for the past two weeks.

Any idea how to solve it?

Thanks

Ohad