Chinese, but not just those students, have a hard time with the word down. It's the OW diphthong, OW, plus the N consonant. And they kind of mix the N into the diphthong and nasalize it. Down.

国人，但不仅仅是那些学生， 很难解这个词。 它是 OW 双元 OW，加上 N 辅。 他们将 N 混合到双元将其鼻化。 吃下。