"DB2 SQL error: SQLCODE: -440, SQLSTATE: 42884, SQLERRMC: =;FUNCTION
Message: No authorized routine named "=" of type "FUNCTION" having
compatible arguments was found. "

this msg is detected because (for some reason) DB2 thought that you like to execute a function named '='. It definitely doesn't come from the insert-stmt.
Some we need to look somewhere else:
1) trigger
2) UDT
3) check-contraint


by all means, the '=' should come from somewhere. which is the starting point