Two side weights do not move anymore

by Carolyn
(Australia)

I have a free-standing grandfather clock which was serviced 12 months ago after about 10 years of neglect. It does not show any branding or marking and is estimated to be from the 1920's.
It has been running/chiming fine since the service, but last time I wound it, only the centre weight drops. The two either side are stationary and the chimes have stopped (usually chimes every quarter hour). It is still keeping time. I stopped the pendulum after a day of this behaviour.
Any help is greatly appreciated.