Hi,
did you try to setup trace in RSECADMIN ? if not please follow below steps to get exact authorization trace which will help you to analyze authorization error.
1) go to tcode - rsecadmin
2) go to tab - Analysis
3) Click on "Authorization Log"
4) Click on "Configure Log Recording"
4) Add user ID to be traced
once done inform user to log out once and try again. now you can read trace data under "Authorization Log"
Regards,
Satyajit