I was so infuriated at the lens hood falling-off Sony A-mount lenses, that I complained about it in a review comment on the Sony website.
A few months later, an email notified me that someone had replied to my review. The reply kindly informed me that the lens hood must be twisted past the first hint of resistance, and would then lock-in-place.
Sure enough, as-long-as I put the lens hood on properly it doesn't fall off ;-)