When I delete files from an SD card, they magically return
I'm having trouble deleting files from an SD card on my 2019 MacBook Pro running Catalina. Previously, to deleted the files on a card all I've had to do is drag the files into the bin, empty the bin and then eject the disk. Trying to do that on my current MacBook Pro, however, I drop the files in the bin, empty the bin, check that the card is indeed clear (using disk utility) and eject. As soon as I return the card to the reader, however, all the files are back. What is going on and how do I stop it? PS It's nothing to do with the write-protect button because if I put the card back into my old MacBook Pro, I can delete the files without a problem (this is not a long-term solution for me by the way).
MacBook Pro 13″