Matador magazine skipping/jumping

My .22 r3m did exactly the same when it was running with too much hammer tension.
It used to skip every other peller
Backed off power a little and now it’s perfect.
Atb j

I’d check the indexing pin, give it a press to see if there’s a spring to it.
Check the cocking plate, there is a small O-ring and screw on the pivot point.
I would check to see if the screw became undone and replace O-ring and lightly lube it.

Also you might consider trying in placing a pieces of aluminum or plastic shim even on the inside of the breech assembly to limit the cocking plates over travel. Using hot melting glue gun to attach the piece so it can be removed when/if needed.

Some took a Dremel to the cocking plate to grind some metal off of the cocking plate, but IMO I’d try the above first.

Good luck !

~ Greg