I have a Seth Thomas mantle clock with a 120 movement I am an amateur and after a little investigating decided undertake (thinking I had nothing to loose) the disassembly, cleaning, and re-assembly of the movement because it wasn't working even though 2 clock repairmen had worked on it after which it ran for a few days, then only for a few hours. I didn't do any mechanical work on the parts,, but just cleaned, re-assembled, and oiled. It actually runs now! (surprised as to why now? ) but have a problem- it strikes on the hour and half hour correctly, but also strikes once at ~8 minutes before the every hour. I figure I must have assembled something in the wrong position or something? Any help would be appreciated.