An issue is that which comes forth from something. A knowledge issue is something that proceeds from the starting point of knowledge — can we know something, how do we know something, how do we apply tests of whether we know something. The kind of question or problem that is a knowledge issue reduces to this kind of question: "How do we know?", "What do we know?", or "How is it that we can say we know?"
And that is all. I cannot believe it has been about 2.5 years since I last wrote something about this. You can find it embedded somewhere in this post