Chosen Solution
The copy DVD stopped playing, was irratic but when I fast forwarded it, it played like the original but with no sound/no music. Original DVD is a dance DVD. I noticed it took a long time (several minutes) to burn a copy of the original DVD. Help!
Get a CD/DVD head cleaner and give that a try for both drives. You may need to burn a fresh disk, make sure the disk is dust & fingerprint free and try using the slower burn speed.