I have created a webhook and am seeing it regularly execute twice, always 5 minutes apart. When I look at the Event log on https://mytenancy.userecho.com/settings/integrations/webhook/, I noticed that on every occasion that it executes twice the log shows a 5 minute gap between Created and Delivered,and on every occasion that it executes once the log shows no gap between Created and Delivered. Below is a screenshot of my Event log in UserEcho and the event log in my consumer (an Azure Function) with the timestamps linked by arrows. Note that in all cases, my consumer responded with 200 OK within a few seconds.
The screenshot was captured after the latest event was created, and was processed by my consumer, but before UserEcho recorded it as "Delivered". In this case, UserEcho sent another request after 5 minutes, as described above, and now shows 9:19 a.m. as the Delivered time and a Status of 1.