Insert Markup is not working in Confluence in a few cases

Issue Summary

A Wiki Markup added via the Confluence Editor > Insert more content > Markup is not being converted properly in the markup Preview and throws the pop-up error below when clicking on Insert:

This is reproducible on Data Center: yes

Steps to Replicate the issue

1. Install the affected version of Confluence.
2. Create a new Space.
3. Create a new Page and insert the Wiki Markup via the Confluence Editor > Insert more content > Markup:

   ||text||
   

   The issue is hard to replicate as it needs multiple attempts to insert the Wiki Markup to the Confluence page in order to replicate the issue.

Expected Results

The Wiki Markup code is rendered and inserted without issues.

Actual Results

The following message pop-up in the editor:

The request /rest/tinymce/1/wikixhtmlconverter fails with a HTTP 400 Bad Request error as the entityId (which is the pageid/contentid of the current page) is not sent to the server.

Confluence access logs recorded the same response:

172.50.0.2 admin [18/Oct/2023:12:32:14+0000] "POST /confluence/rest/tinymce/1/wikixhtmlconverter HTTP/1.1" 400 76 6 /confluence/rest/tinymce/1/wikixhtmlconverter http-nio-8090-exec-5 "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36"

Workaround

Hard refresh of the page will help to preview and insert the markup properly.