Why is it not possible to add two webcams to one OBS Studio scene?

Question

Video broadcast

I cannot add two video sources, namely two webcams in one scene. It turns out to include only in turn. What could be the problem?

Answer 1

Do you have cameras connected to one usb2 port using a hub? space them further apart (if I understand correctly on the motherboard behind the ports also come in pairs or four), which port to insert which camera choose experimentally, ideally use the usb3 port for at least one camera,
two cameras may not work simultaneously in one usb hub due to lack of usb performance or just one of them works with usb skewed