Percentage Of Errors?

I would say much higher. I collect nickels from the wild and after 40,000 nickels I found one major error. The odds to find it was like 1 a few millions nickels. I assume bills would be similar.

From my knowledge, it depends on what you mean by error. Bills with printing errors (missing features, improperly cut etc) are extremely rare in modern bills. However, there is a famous error in the $100 from when they first redesigned it--the watermark was put in upside down on a significant percentage of the bills. Likewise, the new $100 bills were so frequently misprinted that it took years to get the series out the door.

But as others have said, the quality control at the BEP is world-class. I worked as a cashier for the better part of 4 years, and I found plenty of star notes, but not a single error note.