Upgrade required when inserting document into a bucket (python sdk)

I am trying to insert a document into a bucket from python sdk. I do see the document Id in couch base server but when I open it to see its json content, I see “Upgrade Required”.

Is there any more explanation to the error, as to what I need to upgrade? Not sure if helps nor related but if I create documents via sync gateway _bulk_upload, I do see the documents fully/correctly in couch base server.