Hi @FaridKhaheshi we are also facing this same problem. We opened a ticket with Atlassian, they have already replied and said that they were able to reproduce the problem. We are still waiting for more information on when they’re fixing it.
The problem happens like you said, on /enabled webhook, but it also happens if you create the field using this API: /rest/atlassian-connect/1/app/module/dynamic. If you try to search for the created field sometimes it says that it does not exist.
Here a post I also made here on the community: