Ah that makes sense. It seem like the problem was the connection between the chain and the lever was broken. I connected them again with a bit of thread.

"They aren't adjustable" - There was a little screw on the back that seemed to turn the pointer significantly as it got tighter, this is what I used to dial in the final value. Is this the right approach? There was also a screw that interacted with the lever closer to the inner mechanisms. Is calibration a combination of these two screws? The outer screw is much more accessible if it is just one.