Knowledge is never justified true belief (JTB).
Justification is an alleged process that shows knowledge is true or probably true. Knowledge is never justified because justification is impossible, unnecessary and undesirable. If you assess ideas using argument then the arguments have premises and rules of inference and the result of the argument may not be true (or probably true) if the premises and rules of inference are false. You might try to solve this by coming up with a new argument that proves the premises and rules of inference but then you have the same problem with those premises and rules of inference. You might say that some stuff is indubitably true (or probably true), and you can use that as a foundation. But that just means you have cut off a possible avenue of intellectual progress since the foundation can't be explained in terms of anything deeper. And in any case there is nothing that can fill that role. Sense experience won't work since you can misinterpret information from your sense organs, e.g. - optical illusions. Sense organs also fail to record lots of stuff that does exist, e.g. - neutrinos. Scientific instruments aren't infallible either since you can make mistakes in setting them up, in interpreting information from them and so on.
Knowledge need not be true. Newtonian mechanics was knowledge, but it was never true. Also, quantum mechanics and general relativity contradict one another but we don't have replacements for either of them. they are both false but they are also both knowledge.
Knowledge also need not be belief. There is a lot of knowledge encoded in computer programs or books that nobody believes. The point of writing stuff down is so that you don't have to remember it.
Knowledge consists of solutions to problems, not JTB.
For more criticisms of the JTB theory see "Realism and the Aim of Science" by Karl Popper, "The Beginning of Infinity" by David Deutsch, http://www.curi.us/1232-justified-true-belief-speech.