This is one of my fundamental red flags. I'm expected to never reschedule an interview, it consumes both the interviewer and interviewee time, it's stressful and something you generally try to prepare for. If the HR/TA from the company that is trying to hire me fails to join the call it's an instant pass.

I don't know what is your current work or life situation but there are many other places looking for people with similar skills that probably won't disrespect your time.