I haven't codified the exact distinction that I make between those two concepts; in the case of material science, a 'problem' would be a pressure vessel at a low temperature containing high pressure; the failure mode of such a problem would be brittle fracture.

In this case it might also have made sense to call it a class of problems; each instance is different enough that a general solution would be different in nature from a series of specific solutions which combined covered every individual exemplified case.