Oh yes, pattern directions or measurements are often wrong. I know of one designer, who has impeccably written instructions and wonderful patterns. A good friend of mine was one of this designer's testers and my friend has said, more than once, how many mistakes and inconsistencies were in the original patterns and how often a pattern would be rewitten. I don't think testers get nearly enough credit.
As for a designer who will not correct her own work after accepting money for a lesson or pattern--well that's not a very good business practice and borders on just plain rudeness!