I got one of these four days ago and lost it in the subway! I believe the mechanism makes it easier to open up and fall off, as it did in my case
I almost lost one of mine while on travel. I went into my bag and the bangle must have pushed up against something and the push mechanism opened. I have found that the best way to deal with this is wear there bangle so that the push mechanism is upside down facing my elbow. I then stack bracelets on the side closer to my wrist. Haven't had any issues since!