I'm sorry, I wasn't totally clear. Both of those workflows use webhook actions, but I wasn't able to see any webhook-related errors in either workflow. This generally means that the issue isn't with the webhook, but instead with the workflow (e.g. enrollment criteria, suppression lists, etc.).
In order to really troubleshoot the issue, I need to examine a specific contact record that did not pass through the workflow as expected. That will give me more information on what might be going wrong.
Side answer: Workflow webhook actions are useful, but a more scalable solution would probably be to use the Webhooks API (see below). The Webhooks API allows you to subscribe to different events like object creation, deletion, and property changes.