(A) A WU expires so the server declares it "lost" and it issues a NEW COPY of the WU to another machine.
(B) A machine requests a new WU without returning the previous one so the server reissues THE SAME COPY of the WU to the SAME MACHINE
(C) Somebody manually moves a WU from one machine to another or changes the passkey or changes the user name.
(D) A WU is successfully completed and uploaded but a server failure prevents the credit from reaching the stats system through normal channels.
(E) A WU is corrupt.
Case A: The WU is a new assignment to a new donor with no relationship to the previous donor or to any previously issued WU.
Case B: The WU has been continuously assigned to the same donor the whole time so the bonus calculation is based on the total time from download to upload
Case C: When you change things manually you always do so at your own risk.
Case D: The PG has consistently (manually) tracked down and reconstructed any server-based data that can be found and awarded credit posthumously.
Case E: No credit -- especially if this overlaps with case C.
