Suggestion: warn if multiple webhooks
A system check warns if the expected webhook is not found but does not warn if unexpected webhooks are found.
On a system I recently looked at, it had 5 webhooks including one to the test processor - caused by changes in hostname, enabling clean-urls etc. This caused confusion in the logs and may explain other failures being experienced.
So the suggestion is to add another system check job warning if there webhooks configured other than the expected one. The system check can be hidden on any system that actually wants multiple webhooks.