I just got my first Curta (type II) for my birthday and it is perfect except for this odd display error: the largest display digit tends to turn with the smallest turn counter (they are of course right next to each other). I am pretty sure this is not supposed to happen, but I have no idea how to fix it. Although it causes no calculation errors (because the largest digit is never a problem), it does catch a little when I crank it, and I worry that continued use may be damaging to it. Any advice? And to be clear, it is only the largest digit display that is incorrect; the smallest turn counter is simply what it syncs up to. (I hope you will excuse my lack of terminology knowledge)

Ok, so, apparently the catch that prevents people from cranking it counterclockwise is also malfunctioning, as my grandmother just jammed it...I would really like to not break this, so I'm thinking it may need repair. Is Jack still repairing?

I don’t know anything about Jack, but you can try the service operated by Romano. I am fully satisfied with it.
I know that the logistics is not simple and cheap - I think it's worth it.

I have no affiliation with Romano other than being a satisfied customer.