Confluence not able to add inline comments in pages after editing the page

Summary

We had several cases where customers are reporting that inline comments are failing to be created.

A customer reports this is intermittent. In our tests, we could reliably reproduce one day and it would fail the other. So, it seems to have moments where it works.

Also, this is not a system problem, it happens in specific pages.

UPDATE: This seems to happen on pages which have been recently edited.

Steps to Reproduce

1. Go to an affected page (by editing the page and leaving the editor)
2. Add in inline comment

Expected Results

It's added .

Actual Results

We get a 'Could not save comment'.

Workaround

Temporary fix is to flush caches in Confluence.
Cloud customers will need to report to a Support Engineer to run this for them.