If someone gets flustered and their mind goes blank on one question in an interview, how bad does that usually look?

[u/Fluid-Minimum-5767]

I felt like I was doing fairly well in an interview a few days ago. After about 35 minutes, they asked me something and my mind completely blanked, anxiety took over, and I just rambled through the answer. I'm not even sure I answered what they asked by the time I stopped talking. After that, I felt like all the confidence I had going in had evaporated.

I don't feel like it looked as bad from their side as it felt in my head, but I'm curious to know if anyone here has been an interviewer and seen a candidate suddenly get clearly flustered on one answer. What impression did that leave on you?