When an integration app posts to a custom action URL and that action is switched off the app receives a 200 response and the endpoint for the custom action is never called. Please consider to response with 423 Locked (WebDAV; RFC 4918) in these cases.
Just to confirm, I suppose the custom app is triggered by using a custom webhook trigger. In this case, your app’s recipe with the custom action is turned off, but the trigger is still running because you are creating the webhook in some of your apps programatically.
Is my understanding correct? I do think this could be helpful for other use cases as well, but just want to understand the flow here a bit more precisely.
Yes, that is correct. So, the even takes place on the board which results in my app receiving your post to the webhook endpoint. From there my app posts to the action URL and gets a response 200. The action endpoint is never called because the integration has been switched off.