When attempting to update pages via REST APIs, 501 error is returned

My script loops through a list of XHTML pages and creates/updates pages on our Confluence Server. It was working smoothly earlier. Off late, the loop fails at random places since 501 error is returned.
https://confluence.nextgen.com/rest/api/content/168278392
<Response [501]>
{‘statusCode’: 501, ‘message’: ‘Unable to save changes to unreconciled page ContentId{id=168278392}. Refreshing the page should fix this.’, ‘reason’: ‘Not Implemented’}

Does the Auto Save feature interfere with API calls to update a page?