As far as I can tell, quality control for the New York Times crossword puzzle is very good but errors do creep in.
This past Friday, the clue for 37 Across was “Symbol of electromotive force.” The intended answer: epsilon. I’ll admit that the symbol for emf looks kind of like an oversized epsilon, but it’s not one: it’s a capital E in a script font. In over 20 years of doing and teaching physics, I’ve never seen emf denoted by an epsilon.
Oddly enough, the last error I noticed in a Times crossword also had to do with emf. In that case, the error was more unambiguous. The clue was “Energy expressed in volts”, which is actually meaningless: volts aren’t a unit of energy.