So, I've had this problem just about every cuckoo clock that has been brought in. Take everything apart, do all the standard inspections, clean it all up, reassemble, everything works for a little while. Then BAM! The pendulum just hangs up. It drove me nuts for a little while. The pendulum would literally just hang up, it drove me crazy. It would run for a little while, then just stop. You could see the pendulum actually hang. It was insane. I remember it was very quiet in my little workshop, and I got the clock running constant with a bit of extra weight. I heard a very quiet squeaking sound. I got closer to the clock, and sure enough that movement was squeaking with every move of the pendulum. It was very quiet, but I could definitely hear it. After this, I replaced the escape wheel, and verge. This remedied the squeaking sound. I got another clock in. The pendulum hung just like the one before. I also heard a squeaking sound. Did the same thing (new verge and escape wheel). Fixed it. Now I have gotten tired of changing these things. So someone brought me this cuckoo clock a few days ago. Sure enough, the stupid pendulum would hang up. But when it wasn't hanging up, I heard a very quiet squeaking. Cleaned the movement like normal, except for the escape wheel and verge. I removed the escape wheel and verge. I took a small arkansas whetstone, and lined it up with the flat edge on the escape wheel. I then did three solid grinding motions. One Two Three, Next Tooth, One Two Three, and so on. Did the exact same thing with the opposite side of the teeth. Then took the arkansas whetstone, and gave a nice good polishing on the verge until it was sparking. Reinstalled the verge and escape wheel. Bam; fixed. I remember reading here some time ago someone saying that every cuckoo they've gotten has had a squeak to it. I hate that squeak.