TikTok Machine Learning Engineer interview questions

Approached by recruiter with whom I had an initial phone call. Then had a video technical interview. The procedure and logistics was all very smooth. I was asked about my background (with a couple of follow-up questions), then a couple of basic ML questions, then a coding question.

Around early Feb, I received interview invitation. The position is machine learning engineer. Here is my timeline. Feb 12 1st tech round Feb 18 2nd tech round Feb 26 HM round Feb 27 got rejection