It' s not uncommon for my string to slip off when I have my bow in a sock hauling it to a shoot, hunting, etc. A flemish string shouldn' t untwist by itself--I use my thumb as a referance just in case though. I use a " thumb' s-up" with the base of my hand resting on the deepest part of the grip--once you get used to it you can tell if your brace height has moved any.

Chad