The cam stack is busted, boo boo'd, and kaput. If that was normal it would be a nice straight seam.
Now, I know nothing about Necchi machines or broken cam stacks but since you have but $5.00 in it to my way of thinking it's not gonna hurt to try and fix it. I'd try at to at least find the parts, price them out, find a service manual, then decide.
Here is one thing I might try if and I mean if you can disassemble the cam stack from it's shaft. Clean it till it's sanitary, then degrease it and glue it back together with LocTite Black Max. Then use automotive hose clams to draw the edges together while the Black Max cures. That stuff is the best adhesive I've used. It will glue things that epoxy will not and that super glue will not.
It's hard to find though and I don't know how the cam stack is made.
Just thinking out loud.
Joe