OBS hangs. Cameras not updating.

[AndyH]

I'm trying to use OBS 27.0.0.1 on Ubuntu 21.04. I had some initial success with 3 video cameras, but now it hangs soon after starting. The UI becomes unresponsive for 30 seconds to a minute. When I restart it, even after a reboot, one or more of the cameras don't show up. If I delete them and add again, sometimes it works for a few minutes. The computer is idle.

I have the following devices:
E: DEVPATH=/devices/pci0000:00/0000:00:1c.4/0000:06:00.0/usb8/8-1/8-1:1.0/video4linux/video0
E: ID_MODEL=Logitech_StreamCam
E: DEVPATH=/devices/pci0000:00/0000:00:1c.4/0000:06:00.0/usb8/8-1/8-1:1.0/video4linux/video1
E: ID_MODEL=Logitech_StreamCam
E: DEVPATH=/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/usb5/5-1/5-1.1/5-1.1:1.0/video4linux/video2
E: ID_MODEL=C922_Pro_Stream_Webcam
E: DEVPATH=/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/usb5/5-1/5-1.1/5-1.1:1.0/video4linux/video3
E: ID_MODEL=C922_Pro_Stream_Webcam
E: DEVPATH=/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/usb5/5-1/5-1.3/5-1.3:1.0/video4linux/video4
E: ID_MODEL=HD_Pro_Webcam_C920
E: DEVPATH=/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/usb5/5-1/5-1.3/5-1.3:1.0/video4linux/video5
E: ID_MODEL=HD_Pro_Webcam_C920

I have a X99A GAMING PRO CARBON (MS-7A20) with Intel(R) Core(TM) i7-6850K CPU @ 3.60GHz, 8GB ram.

Any ideas on how to troubleshoot this?

Thanks, Andy