After initial contact from HR, I had a technical phone interview.

The interviewer was not ready.

First, at the interview time, he called me to say he was still at home and would call back in one hour.

An hour later, he was ready but not prepared.

He had no idea who I was and no CV in front of him, which made me think: "What am I doing here, and why am I wasting my time?"

Small questions on simple C code (I think to flip an array), followed by some basic machine learning stuff, and ending on some technology he was working on, even after I mentioned I never really studied that particular field.