ScriptRunner Macro's not found when Confluence is restarted

When the Confluence instance is restarted, none of the ScriptRunner macro's are displayed. Instead the user sees "Unknown macro: <macro-key>".

Steps to Reproduce

In your test Confluence instance with ScriptRunner installed:

1. Create a page with some content
2. Create another page and use the "Include Version" macro - link to the page that you created in Step One
3. Stop the server / VM / container running the Confluence instance
4. Start the server / VM / container running the Confluence instance
5. When the server has started, navigate to the page you created in step two.

Expected Outcome

You should see the content from the first page, included in the second.

Actual Outcome

You see the "Unknown macro" error in the page

Scope

Testing has shown this affects all built-in ScriptRunner macros.