XML-20221: (Fatal Error) Invalid char in text

Today while running one of the invoice reports, we got following error

[032610_072720844][oracle.apps.xdo.common.xml.XSLTWrapper][EXCEPTION] XSL error:

<Line 23, Column 17>: XML-20221: (Fatal Error) Invalid char in text.
<Line 29, Column 17>: XML-20221: (Fatal Error) Invalid char in text.
<Line 34, Column 14>: XML-20221: (Fatal Error) Invalid char in text.


XML File was big. It had around million lines. Visual inspection was not useful. We copied the file from $APPLCSF/$APPLOUT/o<request_id>.out to desktop and used template viewer (start->all programs-> Oracle BI Publisher Desktop-> Template viewer) to view the xml file. XML viewer gave errors and the line numbers that were in error. Those lines had control characters. We fixed those invoices and report ran fine.