On the interviewer side of the table, I had a candidate and there was a stretch of silence after they confirmed they understood the problem which I interrupted with "Is there anything I can help clarify?" (I can't observe internal state!) They asked me if I could be quiet for 5 minutes while they thought about the problem. That's fine, I did so. Maybe you can ask the same thing next time if interruptions come too frequently? If they don't respect the request to shut up, that's a useful signal to not work there too.

Lack of interviewer experience can also account for some of it. Unless everyone in a room with more than one interviewer has their turn at questions, I'd expect the silent ones to either be shadowing so they can interviewer, or be overseeing a former shadow take the reigns. I think an interviewer needs to do as little as 10 of them to run the style range of people who need some quiet time to silently think, to people who ask lots of questions, type some, ask more, type, to people who easily vocalize all their thought processes while typing things; the interviewer may also importantly see that despite the style differences the time to get to the same place (if they get there at all) doesn't vary by much...