Webcam start/stop buttons not working

I'm experiencing issues getting my webcam stream to stop and start through Octoprint. I followed the instructions exactly, as detailed here: and the webcam starts up automatically during boot, which is good. However, selecting "Start video stream" and "Stop video stream" in the power menu returns "The command executed successfully" but doesn't actually do anything.

I'm running Octoprint 1.3.8 via Ubuntu on an Intel NUC.

Any help or ideas would be appreciated.

Stopping the webcam appears to use the pkill command within the /home/pi/scripts/webcam script. I wonder if the pi user has rights to do that? Guy did some interesting things with the sudoers configuration to allow pi to run shutdown and reboot, for example.

@foosel Is it necessary to do the same for pkill?