It is quite confusing, but she worked for US game and fish in 2019 and then transferred to US forest service.  After the transfer, game and fish contacted her stating that she was paid for a pay period for which she had already left their employ.  She was able to prove when she left employment, so because a bill had been generated in their system they decided to pay her the amount she owed, and she had to give it back upon deposit of the check.....now, she has received a W2 for 2024 for the amount paid, including social security and medicare withholding.