I saw three examples of this in one day! Two in the New York Times! Example with discussion below:
Name your second-favorite airport- or airplane-based movie.
“Die Hard 2” was certainly was an influence.
—from interview with T. J. Fixman, writer of Netflix movie Carry On
Just a general discussion because I don’t know how to rate errors like this, annoying to read as they are. Your eye might have skipped over it. In the author’s response, the passive verb was gets repeated before and after the adverb certainly. Presumably when first typed, the writer of this sentence wasn’t certain whether to split the verb from its descriptive object influence (called a subjective complement to be exact). Did this occur because the author thought the editor would pick the ‘right’ one? Technically both are correct, but I could make an argument for “certainly was”. Is the author self-editing, and planned to come back to this? Or, as I fear most likely, did the author have a brain-fart, being unable to carry the sentence construct mentally for only three words?
Twice in one session of reading, New York Times? When I saw a third one on a sports blog, I couldn’t believe it, but at least it’s written by dedicated amateurs more interested in sports than writing. I can’t rate it because it’s egregiously wrong, yet quite possibly represents a case of just typing too quickly and hitting ‘Send’.