I initially said that I would start poking around in the code and they revealed that they were talking about proprietary software and that I couldn't look at the code. I then responded that I would try to decrease the size of the data set and keep making it smaller and smaller until there was no data left to see if that caused the error. It turns out that this would work, but then the interviewer wanted more specifics about how I would down select the data set. He seemed to think that I would only remove on row at a time instead of halving the data set each time ore something like that. I think this is a really dumb question for lack of a better more descriptive word. They were trying to determine my problem solving abilities with a tool that they are intimately familiar with and that really only exists in their industry and in addition, wanted a very specific answer. It is like if I asked you to debug a photoshop issue when you have never used photoshop before, but maybe you have used video editing software, but I wanted the exact answer for a specific photoshop bug. I am assuming the error is trivial for anyone who has used the software but it doesn't tease out problem solving ability if you have to know how the software already works and the software is not common place or would be known by someone coming in from another industry.