Steps to reproduce:

1. Using Firefox, Log in as a teacher and access a course page you can edit.
2. Turn editing mode on and open the tab drawer if required.
3. Click "Add a block" -> "Text..." and wait for the modal form to load.
4. Press Tab
   • The "Close" (X) button should be focused
5. Press Tab
   • The "Collapse block settings" button should be focused.
6. Press Tab
   • The "Text block title" field should be focused
7. Press Tab
   • The "Content" editor field should be focused.
8. Press Tab
   • Expected: The "Save changes" button should be focused. 
   • Actual: The modal is focused.

This happens in other modal forms that include an editor field. It does not happen if the user is using a different editor plugin (e.g Atto).