The serrated blade on my Wave did the same thing a few days ago, right after I accidentally dropped it in the dirt. I dribbled some Breakfree on the hinge, hit it with some pretty high air pressure from a compressor, nothing. Then, after a few days, and a lot of openings/closings, it suddenly started working fine again. I assume that a little grain of sand or something got inside, and is just took a bit for it to work its way out...