I am guilty of not paying attention to this detail that can dramatically reduce the force a biner can handle.
From the American Alpine Institute’s blog:
Surprisingly, there is one mistake that both beginners and advanced climbers alike tend to make. Many people will wrap a tree with a sling and then clip the sling. Often the sling is wrapped around the tree in such a way that it is loading the carabiner improperly. A carabiner that is loaded from three directions is often referred to as being triaxally or tri-directionally loaded. This is very very bad… (link to the article with pictures)