Looks to me as if it’s resting on the grip on its front edge. Pull the grip and see if it goes down further and “snaps” on the detent. If it does, remove a little material from the grip to allow it to come all the way down. CM is a damn fine gunsmith, so listen when he talks…This is as far as the thumb safety allows to be pushed, and it is very loose going up. I get the point about keeping the thumb on top of the safety lever, but I thought it supposed to lock in place instead of being so loose.
Edited to add:
So, I went back and actually read the thread, and I think you’ve already found what I saw…trim the grip just a bit…
