Gilbert 1807 Chime is all messed up

(Gray Court, SC)

My wife has a Gilbert 1807 Mantle clock that if you try to set the chime to the hour sometimes it chimes 24 and sometimes 2 sometimes 10. We followed the instructions turn to 12 back to 8 then to 12 we get the above results. It does do the 1 chime on the half hour. Please Help