I had to have to recoil lug resoldered on my 21.

It didnt seem to be "spendy"
A gunsmith by the name of David Yale in Yellowjacket Colorado did it for me, along with the required reblue of the barrels.
He did a remarkable job! and pretty quick turn around too.

Check the forearm lock also,, and make sure it "snaps" in place.
There is a mark on the little wheel that disappears and "snaps" when its locked in place.

Gooser