In 2003 we migrated from V4R5 to V5R2 and had SQL “issues”. Can’t remember exactly what they were but I have an archived email that says the solution was the deletion of QGPL/QZDAPKG *SQLPKG. Once deleted this is recreated by QUSER and solves the problem – whatever that may be.
Apologies for the rather un-specific help but it might solve your issue – it can only still fail, right!!!