The cardinal #digipres sin, the one that'll make preservationists scream:

"We tested the {tape/disc} in a machine so we didn't waste time making an image if it was bad. After playing the game for a few hours we found we couldn't load the tape again."

Lesson here is, take the image first, you can always write it back to a new tape, but that one read may be your only chance...

(the above sin was committed by a museum ... sigh)