Macro within another macro is broken after the second user saves the page

Summary

When a page has one macro within another macro, let's say a Warning macro within an Info macro, and at least 2 users are editing this page at the same time, and both users save the page, the macro within breaks after the second user saves the page, see screenshot.

Steps to Reproduce

1. Create a page
2. Add an Info macro and within the Info macro add a Warning macro
3. Save the page
4. With one user, edit the page
5. Access this page with another user and also edit the page
6. While both users are editing the page at the same time the first user saves the page, and the second user also saves the page right after

Expected Results

After the second user saves the page, the macro within the other macro, on this case the Warning macro, should still be viewable

Actual Results

The macro within the other macro breaks. A message saying "Broken macro" is displayed

Notes

There's no need for both users to save the page at the exact same time (instantaneously).

Workaround

As a workaround, when a User edits the problem page, the user can add an edit restriction for the page and restrict editing to themselves. This restoration will need to be removed after editing the page. This is a rather tedious workaround, but it will prevent the issue until the problem is resolved.

NB: In the unlikely event that anyone experiences this issue post 5.10.4, it is because the macros were entered on the page some time ago, before macro ids were used. If this does occur, the workaround is to revert to the old version, then save the page (ensuring no one else is editing it at the same time). Once a single-session save has occurred, the macro will have an id, and the problem will be solved for that page forever.