You're effectively asking it to invent a rationale for what you are telling it was the thing it told you last time round.
Asking it to "think out loud" during its initial answer is a better way to get insight into why it answered in a particular way (and also often causes it to provide better answers).
Asking it follow-up questions is almost always useful, it's just the "why did you say X?" pattern that I'm recommending against.
Completely separate interaction maybe. You can certainly ask a question then ask it to rephrase the answer, etc. Like "say five words", followed by "reverse the answer"...produces the same five words in reverse.
Asking a question then following with "why did you say that?" usually cites the previous context reasonably.
There’s lots of evidence that this is what people do, too. Asked about their reasoning, people will do things like include information they didn’t have at the time. The part of the mind that moves the fastest doesn’t encode the process to memory[0] but we’re really uncomfortable saying “I don’t know” about our own decisions. So, we rationalize.
If you want to be more accurate, you need to do the same thing of “thinking out loud”, either subvocalization, voice or paper. Even then it’s not perfect. Easy to make up your mind and justify it after.
[0] Which, of course it wouldn’t. You don’t log every line of your fastest piece of code. Then it’s not fast.