I've been working on a project my director gave me, he gave me a bunch of pads and a clarinet that needed repaired. I have all the pads in, I oiled it (it was wooden), and I replaced a few corks. Everything works fine (after using a different mouthpiece, as the mouthpiece was wooden and fifty years old, and wouldn't play anything), except the keys for C#, C, B, and Eb in the upper register. They work fine in the low register, but once I pop up to the next register, those notes, and those notes only, don't work. What could be the problem? Note: I did have to take all of the keys off and put them back on, if it could stem from that.