I added a new custom webhook integration today 66ec2d2afed79e14a9a64a5d
When I selected 'web form' I could not save the integration until I clicked 'custom' under 'form fields'. This of course made it so no data was passed. I then had to go back and select 'default' under form fields and then save to get the default data to be passed in the webhook.
Not sure if anyone is aware of this, looks like a form validation issue on the UI maybe.