Problems re-scanning songs in database

[Roy Dennis]

I expect there could be numerous reasons, for instance if a hard drive got an section error then the file in that spot would be damaged.
When you do a hard drive check it normally repair the hard drive section but it may not repair the file that was on that part.
Files can still be damaged, I think you may be confusing it with copied files stay at the same quality as the original unless you compress it more than an original.
But with the old tape recordings, every copy lost something from the original for each copy you took.