The point about maintenance in the discussion I was trying to make was that a sidelock would, with more moving parts, need more of it, than a boxlock. Nothing more. I had a worn out sidelock when I was a younger man. If it was from lack of maintenance, or much use, or, much abuse, I don't know. Since I bought the gun, here, in the US, use with ammunition outside of the gun's design parameters is suspect, but, I have no proof. It was purchased as a project gun, and sold the same way, and likely is a project gun, somewhere, to this day. This was back in the 1980s. We have a better grasp of what a gun of that design and level of proof should be fed for ammunition today.
I would like, someday, to try owning another sidelock. A real sidelock, inspite of the fact I got burned, once. The trouble I have is a boxlock does all I need at a much lower price of admittance.
Well, that, and I'm cheap.

Best,
Ted