How to remove collapsible stock button?

https://preview.redd.it/ns46m4syyshe1.png?width=1148&format=png&auto=webp&s=c15808c826d30c80a8ab8b36c9012f053cfb227c

Hey guys. Anyone has experience removing the stock button from the assembly?

Here is a diagram of the stock assembly. Both part #16 and part #19 looked like the retaining pin to me. I have tried to using hammer + pin to punch part #19 into the direction of the base pad of the stock but the pin does not want to move at all. Did I punch it in the wrong direction? Or could part #16 be the retaining pin I should remove?

For reference, this is the guide I followed to punch out part #19

https://preview.redd.it/qv966x630the1.png?width=810&format=png&auto=webp&s=0614e3b41fda4bb20125b102f76ee07639f1478b