Angie, I wish I could give you an explanation but I'm as perplexed as you are. These do not fall off my feet at all. One thing about them is that they are extremely flexible and soft. I guess the fact that they are cheap made them work in my favor, since they lack a lot of the stiffness and structure of more expensive shoes. I still added a heel insert just to keep my heels cushioned but they stay on without them, even when my foot is relaxed. Usually when I cross my legs in ballet flats, the heel pops off and the shoe dangles on my toes...but not with these! Also, as I said, I sized up to a 38! The 37's fit but were tight, and I thought if I went up to a 38 they would fall off...and yet that didn't happen.
The FL shoes were the same ones you got. I think if they had a 36 in stock I would have exchanged them. Oh well, Laura will make great use of them and I'll use the payment she sends me to get a sweet pair of loafers, so it all worked out