I've had such issues a couple of times, both were related to issues with the destination drive. Once it was a misbehaving backplane (or cables, we replaced both), the other was a funky hdd I have in a lab. Try to replace destination drive.
Start with one thing and try again. If the problem reoccurs try the next. Change one thing at a time, that way you will know what's broken.
Personally I would start with the stick.