Ah, I read you now, thanks. I may have reflected on one interview that went particularly badly, being somewhat reminded of it. But with the extra information, that is a great approach if I understand you correctly - especially the silence adding pressure part, which is absolutely true.

I.e. if stuck at something, even if seeming trivial, it might pay (to go back or have a chat around it, even guide him/her a bit so as, etc) to get the candidate loosened up and feeling safe which should then yield better responses after.