I've seen problems with the verifying too. Only when I saw it happen, it wasnt because of over daubing, it was over gluing!
You know how some ladies glue their specials together with paper cards? So they stay put while daubing....
Well, this lady used so much glue and she glued right over the numbers (printed on the sides of the card at this particular hall - which is uncommon and she hadn't noticed it unfortunately)
So, they had to seperate the cards to get the numbers and of course the paper tore, and the numbers were unreadable, so she was not paid either. They did give her a "consolation gift" of a box of chocolates and a vertif for $5 off her next admission

hooray