There is a small bug in the webhook registry area. (Recently tested this on Otto FMS 4.7.0)
If I add a file that has a space in the name, it shows up in the registry with a space instead of %20. Then when I test the hook, or run the hook from my application, it creates a new line in the registry with the correctly encoded file name and all traffic appears to go through that hook instead of the one I created. Clicking to edit that hook shows that the API key is undefined and can’t be selected. However it appears to work just fine.