Hi Sai,
Could you please check and confirm if you have user defaults action from the request type..?
As highlighted in the note "you are using "System" as one of the fields in setting the conditions for User Defaults, then try using the option for Implementing a LOOP in your BRF Rule. This might be needed since "System" field is not available under Request Header attributes, rather it is available as Role Attributes which are called as line-item fields while calling the BRF Rule. So, in such cases LOOP is a suggested solution, rather than using the Decision Table directly. Though within the LOOP, you can still call the Decision Table or implement IF/ELSE conditions."
Better paste some of the snap shots from your BRF+ configurations.
If you are sure enough that your config is on right track then raising this concern with SAP might be an option.
Regards,
Ameet