So far it has happened with two models: the Caly3 CF and the Sage 2. Don't get me wrong, I really like these two knives, but there are some issues that are letdowns.
Caly3 CF: great shape and size, wicked edge, but the outer layers of the laminated blade are too soft and scratch easily, especially at the tang due to friction with the liners (tried every type of lubricant I could lay my hands on to no avail). From a favorite knife, it became a real eyesore in 4 or 5 months of carry, too ugly for EDC. If it wasn't for the scratches, this would be THE favorite Spydie for EDC.
Sage 2: great knife in every aspect... except I cannot get over the RIL. Got it for Xmas and have been EDCing it since. But the RIL is just not for me: it is aesthetically displeasing (the cut in the locking handle make it unsightly) and just feels wrong in my hand (there is loss of purchase in the open position, the locking side just feels wrong). I'll continue to EDC it for a while to see if those issues can be overcome, because I like everything else about this knife.