Custom dynamic content macro editor not reliably shown

Issue Summary

Apps are able to declare dynamic content macros with custom editors, however, some testing shows the standard macro editor is sometimes shown instead of the app's custom editor.

This issue was raised from https://community.developer.atlassian.com/t/default-macro-editor-rendered-the-first-time-instead-of-custom-editor/49357 which includes a screen recording displaying the issue.

Steps to Reproduce

1. Create an app that provides a dynamic content macro with a custom editor and declares on macro input parameter. For example, use the app https://glitch.com/edit/#!/dx-custom-macro-editor-app?path=connect.json%3A20%3A32, which can be installed from https://dx-custom-macro-editor-app.glitch.me/connect.json.
2. Insert the macro in a page.
3. Open the macro in edit mode and observe which editor is display;- Confluence's standard macro editor or the app's custom editor.
4. Repeat steps 2 to 3 as necessary.

Expected Results

At step 3, the app's custom macro editor is always shown.

Actual Results

At step 3, the standard Confluence macro editor is sometimes shown.

Workaround

None