Heres what I think happens; the nut is about 1/2 inch wide and your wrench is narrower so after they have been tightened a few times the nut gets mushroomed and wont clamp against the ferule. Ive had this problem many times over the years so I keep extra nuts and ferules in the tool box. You can get them at Ace Hardware pretty cheap. I agree the weld ins are better, they are typically a little taller and steel instead of brass