Glad that you got the door open Phil,
Well done for not damaging the door card.
The bronze globe - which is actually the electric motor (solenoid) - can be dismantled from the plastic 'rack and pinion' assembly and cleaned. There are three little 'claws' on the bottom of the bronze outer case which can be carefully freed off and the casing can be slid off of the internal windings. You'll probably find it full of crud. Clean it out the best you can (I found good ole WD40 worked best
) and refit and I'm sure it'll be ok until you can find another better one.
Your mechanism here looks pretty good, but mine were gunked up with the black Crylagard sticky oily waxy goo which was supposed to stop the metalwork rusting, but just made things sticky and difficult to dismantle
I often had to strip the motor as I couldn't afford the price of a new one, and the simple fix above saw the locks working for quite a while before I had to repeat the process.