Error stopped the image file transfer

Hi all! I was manually copy-pasting a Photos library from one MacBook (10.14.6) to flash drive to free up the space. However, I encountered an error that stopped the transfer. Moreover, since these files were on desktop, I tried to move them back into the original folder and that failed as well. The size is 15 GB and I do not really see why would these failures occur at all in the first place. Did anyone experience a similar problem?

Hey there!
Check this link
It shows many solutions, from simple ones to more intricate ones
https://www.easeus.com/todo-backup-resource/the-device-has-either-stopped-responding-or-is-disconnected.html