Triple locking karabiners are standard for PPE (Personal Protection Equipment). No one doubts this. Use triple locking karabiners!
We should check them daily for signs of wear and a good test to see if the spring mechanism is working OK is to hold the gate in the position shown in the photograph. If it shuts from here the karabiner is OK. If it doesn't we can add a lubricant like the graphite powder shown in the photo. If it still doesn't then we need to label the karabiner as 'not fit for purpose'. I wrote 'NOT PPE' on mine and it has been relegated to tasks like holding my water bottle or hammock.
＊PPE(Personal Protection Equipment)