The error you get is because for that employee, the return value to operation VARGBTSTID is a value that is not defined in ZEP2 (you have *, CPPL, ECPL, KCPL, KRPL, NDPL, etc... but not the value it's getting from that employee).
As mentioned by every one else, you could add return value **** to your PCR, but you could also look at what value exists in TSTID for that employee and add that value in ZEP2 (with the appropriate processing) on top of adding **** for all other values (with the appropriate processing).