It might be a generic "beep" error that a dirty sensor or paper would normally indicate. People get used to false positives quickly and start ignoring them. Ma

It might be a generic "beep" error that a dirty sensor or paper would normally indicate. People get used to false positives quickly and start ignoring them. Maybe it was a different alarm with a distinctive indicate that "I read this fine, but it's a duplicate" and they would stop and start checking the ID.