My experience dealing with customer support is that there is almost always an actual problem when a customer complains. They often don't know the right words t

My experience dealing with customer support is that there is almost always an actual problem when a customer complains. They often don't know the right words to use, and have no idea why an issue is happening, or they might come up with a completely wrong explanation. So it's easy to dismiss their concerns by saying things like "this doesn't make sense" or "it works on my machine". It's only when you start digging deeper, investigating what exactly the customer could mean, that you eventually discover the root of the issue. Of course, these investigations are time consuming an expensive, often the customer stops following up with you, or you might not understand the behaviour well enough on your own. So very often you don't find the underlying cause. But calling someone a liar just because you can't reproduce their problem is short-sighted and stupid.