The Custom Webhook show an error if it doesn't like any of the custom field keys. This is great, but it often shows false positives, particularly with:

{{contact.id}}

{{contact.name}}

{{contact.last_name}}

{{contact.email}} (YES even this!!)

These errors can be ignored, because these merge fields WILL send the correct values.

!!! HOWEVER: Custom Webhook will ONLY display errors sequentially - ie. you have to fix each instance of what it believes to be an error before it will show you the next field it doesn't like.

Please: