Description of Problem

If multiple users are editing a page at the same time, some can receive the below pop-up warning:

Error saving draft. Last draft saved at 10:30 AM

Cause

Confluence attempts to auto-save drafts of the page using a rest API call to /rest/tinymce/1/drafts. This call happens roughly every 30 seconds after a change is detected. If multiple calls for the same page ID happen at the same time, this will cause the above error. Essentially, if the first call is not done processing, the second (for a different user) will fail. The atlassian-confluence logs will show the following error:

Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1

The stack trace for the error can be slightly different depending on where in the processing the collision occurred, but the above should be consistent across all errors reported. The /rest/tinymce/1/drafts endpoint will also display a similar error if you inspect it using your browser.

Workaround

None at this time. On the next auto-save of the draft, it should hopefully complete.