How to fix this issue ?
Read the data using the correct character encoding. The error message means that you are trying to read the data as UTF-8 (either deliberately or because that is the default encoding for an XML file that does not specify <?xml version="1.0" encoding="somethingelse"?>
) but it is actually in a different encoding such as ISO-8859-1 or Windows-1252.
To be able to advise on how you should do this I’d have to see the code you’re currently using to read the XML.