1. Can you record your webcam through the 'Device Recording Mode' of Bandicam (https://www.bandicam.com/how-to/video-capture/
2. If you can't capture the screen through the 'Device Recording' mode, 1) please disable/uninstall other webcam programs, 2) install a suitable device driver and 3) select another video size at the 'Format' menu.
Please let us know your result.