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Another thing that works for me is opening the razor so its straight out and tightening it with the blade there.

On the back side there should be a tiny bit more pin sticking out of the washer you can peen.

And when tapping the pin don't tap it dead center, you will want to tap around the edger with the ball peen so it mushrooms the pin a bit more. Some newer razors are a pain for me with the lock...