Steps to reproduce:

Create a new wiki macro by creating a page and adding a WikiMacro object. Set some macro id, title, allow inline mode, make it visible to yourself, make the content optional and set the content type to wiki. Set the code to

(((
{{wikimacrocontent /}}
)))

Create a new page. Start writing some text and then while the cursor is in the line of the text, add the macro you've just created, set some content.

Try saving:

Expected result:

The page can be saved.

Actual result:

The page cannot be saved.

Alternatively, just import XRENDERING-745.xar, open the page "Saving Test" in the WYSIWYG editor and try saving it.

Note that this also demonstrates XWIKI-13997, the difference here is that saving fails. Fixing XRENDERING-517 would fix this, however, this is more difficult. This issue is only about the fact that saving fails, not about the broken content.