SQL Job fails due to QUOTED_IDENTIFIER = OFF
Clearly something has caused this to be changed

SET QUOTED_IDENTIFIER must be ON when you invoke XML data type methods.

This can be set at the ODBC/OLEDB/ADO.NET layer, or at the SQLAGENT

MSSQL Client Config 

Something changed the SQLAgent script or modified the Job parameters

If there is script running that alters the stored procedure and dropped the SET command.  Yes that could do it..  Why would this stored procedure need to be altered??