Little did I know when I replaced the switch last year that this one is nothing like the one I took out.
This is the one, like has been described as internals of a clock, with cogs all over the place.
Anyway plenty of contact spray and now nicely ticking away at the correct rate. As a belt and braces approach put it in an ultrasonic bath in case was some junk in there I could not see. Another spray with cleaner and is working a treat.
Was somewhat surprised to fine one of the cogs is plastic as all the other bits seem to be brass or copper.