Clock getting louder and quieter

I realize this is an older post. Hopefully you have found the solution. I had the same thing happening on my SP2 clock. I found that one of my gears was grossly out of balance. I had been having some trouble printing the gears with the filament I was using. If there was a lot of retractions it would tend to clog the nozzle. In this gears case it apparently had a partial clog in one area of its circumference. The material in that area had voids and was much lighter than the rest of the gear. I noticed it wasn't printed very well but it was on the back side of the gear. Since it wouldn't be visible I used it. Just like your clock I could hear the sound varying as that gear went through a full revolution. I took it out and confirmed it was badly out of balance. I added layers of CA glue to the back of the light side and drilled small holes partly into the back of the heavy side to balance it. After I reinstalled it the clock ran fine with a consistent sound. The clock ran with that gear for a long time. I eventually reprinted it while I had the clock apart to add some of the improvements Steve recently provided.