Yes, that's not in the RAW but until there is errata it's my game and my game table and if it's impacting everyone's enjoyment then it will be addressed.
Actually that is exactly RAW. The GM adding setback dice as he feels appropriate based on circumstances. The individual circumstances are not listed but are left up to GM discretion. I think your example is a very applicable and appropriate stance. You as the GM assessed the situation and added dice as you felt conditions warranted.
Yes, I know we can add setback dice. I was referring to limiting the number of attempts, because, as they have pointed out, by the RAW doing the same thing three times in a row is legal. Me going, "No, I don't think attempts 2 and 3 are going to work because they are the same as attempt #1" is against the rules as written; it's my judgement call and I fully expect my player to argue and it'll turn into setback dice or upgraded difficulty, or ....