How can I resolve this error during a dmg copy operation
You can try copying the data using Terminal 

Type in sudo ditto ~/sourcefile ~/Destination

Replace "~/sourcefile" by dragging the file you want to copy into the terminal window which will autofill, and do the same with the "~/destination"

Alternatively: sudo ditto -V ~/sourcefile ~/Desktop
This will show you progress and any errors as the files are being copied