Adding new games to Nintendo64

[Deffo]

Hi everybody,
I am running recalbox on a Raspberry Pi5. I added some ROMs by copying them to the n64 folder via SSH, and they work fine. But if I repeat this procedure a second time to add new games, then every game stops working and after failing to start shows a message that says that the file is corrupted.
Am I doing something wrong? What is the correct procedure to add new games?
Thank you