No, not a bug.
When you do the hover-over translate, it tells you what each word means in the order they appear, but that may not be the best translation of the sentence as a whole. (Occasionally it'll do a phrase, but even then it's just part of the sentence, not the entire sentence.)
"How well you do play" sounds like a statement in English, but this is a question. To get it in proper English you have to rearrange the words to indicate the question. Thus: "How well do you play?"
Another example: if in Spanish you got the phrase "el coche rojo," the hover-over translations word by word would tell you "the" "car" "red." But in English, the adjective comes first, so the translation for the phrase is "the red car."
Does that make sense?