Uhm
sorry but SY-REPID has the value of the current program, so if it's check in a function module, SY-REPID will have the name of the main program of the function group so it'll be the same if the function is called by RFIDYYWT or your Z-copy.
The enhancements are linked to the main program RFIDYYWT , so you should copy them too in your new copy.
I mean you should manage SY-REPID only where it's used directly by RFIDYYWT