Without knowing your exact answers but based on what you've said I suspect you've got some good technical answers but perhaps didn't show how you apply it.
Like the Caldicott bit sounds like you know your stuff but did you give anything about how you would do it? "maintaining patient confidentiality is important because blah blah blah, we can protect patient confidentiality by only discussing work within work and not in any patient areas where I may be overheard, only discussing relevant information with colleagues that are directly involved, etc etc".
Like if I sit round round a table in the canteen and talk about Jane Doe whose foetus is at high risk for Downs and I looked at the cells earlier and there's definitely 3 21s so she might we well abort I'm
a) being rude and disrespectful about an unborn child
B) Jane might be in the canteen, I know she's a patient at our hospital so it's not out of the realms of possibility,
c) Jane's friend/family might recognise what I'm talking about and tell Jane
d) if that happens she's got a diagnosis not delivered by her clinician who would have divulged this information
E) It's none of my business if Jane decides to terminate her pregnancy off the back of this information, I shouldn't be stating an opinion even if I have one and certainly not where I can be heard.
That's a really extreme scenario but I was trying to go for something really bad to highlight the breaches of confidentiality there. STAR is a good technique for this kind of interview to just shove in some examples of how you would do the thing in the question.