After a good question, the easy thing is to talk over the answer. Let the silence sit for a breath, then go back to the one word in the answer that was carrying the weight. There are three simple ways of doing it, and you rarely need all three.
Hand the word back as a question, and then wait
Ask about the last time it happened
Ask what it costs
The HR director of a retail group says: 'Getting new starters up and running is a bit hit and miss.' Which reply stays on the answer?
"So onboarding is a real problem for you?"
"Understood. Who else would be involved in a decision like this?"
"When was the last miss? Walk me through it."
Asking about the last time it happened keeps her words and gives her one real occasion to describe, which is easier than a general problem. 'A real problem' sounds like staying, but it swaps her words for yours and asks for a yes, so you learn nothing new and she may feel pushed. Asking who else is involved is a fair question for later; asked now, it leaves 'hit and miss' behind just as it got interesting.