Thank you for assisting. Let me try to be more clear.
The new fields have been added to the XSN template and when I use propoerty promotion then publish the XSN all seems ok until, i create create a new document XML (via IPFS browser) from the XSN template then error occurs when I try to save the XML back into the sharepoint. If I don't property promote the fields--- the XML can be saved without problem saving the new content in the XML. The error only occurs after promoting the fields. In total it is about 30 new text fields, none required. They all have names like A1, A2 . . . A8, B1, B2 . . . ., C1, C2, etc.
Could the names of the fields be an issue?