The problems with the elenchus method?

One of them is a difficulty that was first noticed in the Meno dialogue. That problem was this: in order to use the elenchus method to discover the answer to such a question, the method must offer a way to decide which of two final answers is correct, and this is not something the elenchus method can provide. Why? The other problem with using the elenchus method to explore answers to “What is F?” questions is vividly displayed toward the last part of Book I of the Republic. What was that other problem that makes this method incapable of providing a means for coming to an answer?
I need a 12 sentence answer with no citations.