Yep I’ve had this. Two issues:
– my old helmet had suffered a direct impact with a large Boulder (unfortunately my head was inside it at the time, but I was more concerned with the broken arm). After that it would release constantly so I got rid and got another one.
– next trabec, it kept doing it, however I discovered that the clip can be moved further down the back of your head over the little bump but that sticks out half way down the rear of skull. If you get it below that it then doesn’t release.
So, check for damage, and if all ok, try moving the retention clip and see if that helps.