@maioni What is your hardware? What's your version of Recalbox (say the version, don't say "the last one")? Did you build your Recalbox yourself, or download a ready-made image from the internet, or did you buy everything ready? How are you trying to transfer to the SD card? Using an adapter? Over the network via SSH? Are you sure the problem is not with the adapter or your network? Are you sure that the problem is not your 512 GB SD card? SD cards must be quality and class 10, or you will face several problems ... I must inform you that the Recommended is to use Recalbox on a small SD card (8gb for example), and to use a pendrive or external HD to store the ROMS and other things. Maybe it will help you: https://www.youtube.com/watch?v=skeULeTu7p8&list=PL2oNQ0AT7fx2ExiSNrfHUzga5GnogI4sh&index=23&ab_channel=Recalbox