I have a Bargello pattern that had some confusing instructions. There was an email address and the two ladies who created the pattern, in Australia, answered my question in just 24 hours. I actually thought there was an error in their instructions, but when they explained it to me, I had just done some sideways thinking.
I thought it was sweet to get such a good answer and so quickly. They invited me to ask more questions if anything wasn't clear to me.
The only other time I found mistakes in a pattern, those corrections were available at the website.
So all of my experiences have been good, along these lines.
Dina