I have periods like that with other stuff. It's usualy a product of rushing, corner cutting (no pun intended), or just being in the wrong mind frame gets me out of the groove.
Walk away from it for a bit is a good idea and take a step back, work on something easier and practice your technique. Not that I'm a knapper, yet. But in general that is what has helped me with other stuff, Carving, technical trading, bow making etc.