I have found a counterexample to the main theorem of a 20-year-old paper. The paper does not seem to be well known but it was written by reputable mathematicians and published in a highly regarded journal. I believe that the main theorem is "mostly true" and the authors simply forgot to add hypotheses to their theorem which would exclude my counterexample. I am interested in applying their results in another paper, but I can't really trust the results.

The paper in question is very long and involves a great deal of technical machinery with which I am totally unfamiliar, so checking their proof in detail is out of the question. Also, an e-mail to the authors went unanswered.

Would a question along the lines of "To what extent are the results in Paper X correct" be appropriate for MO? I would genuinely like to know the answer to this question; however, I would be surprised if anyone other than the authors could answer it in a reasonable amount of time. Moreover (and more importantly), I question the appropriateness of publicly calling attention to the mistakes of others, especially when I am not prepared to fix them myself.