I am sure you are already doing this and the "what their pain point is" phrasing of this post is only for succinctness. In my experience, asking a practitioner about their pain point is seldom the starting point for an unbiased conversation. It can often lead to a freezing of ideas while they try to look and find such pain points, but more importantly here, you are asking them to have identified the problem in a way. Far more effective would be to completely eliminate the word pain point and focus on descriptives like longest or most error prone task, only as confirmation ,after observing for a while. Again I am quite sure from the later description of your question that you are doing something like this, but putting this out there to emphasize the importance of it.