Sounds to me like one or more switches on that mech is now out of adjustment.. but no doubt you have already checked that ?

Yeah, everything seems to be opening and closing as it should. I did spot one of the switches is ALWAYS closed. This was in the small hours so I am going back there to check it out tonight with the schematic. I am not convinced you would have a switch in an always closed position, or why the switch at all. Anyway, will see how it goes tonight.

Ta.