Translation:The solution to the problem is difficult.
Why does solvo mean solution and not "the solving"? It is a nominalization of the verb solvi, ĉu ne?
Another sentence that, when I rephrased it as I would in normal speech, I got dinged.
I think this should be "The solution to the problem". It sounds incorrect to use of in this example as it sounds more like a literal translation.
That's what I got dinged for, and I reported it, and the Owl hasn't quite solved the problem yet.
I recommend reporting it to Duo, and hoping that they realize they are being part of the precipitate.