mine is perfectly fine but a buddys was soo loose he could actually shake the phone in his hand to make it fall off.
so the solution i did was i took his battery out then cut a buisness card to fit under the battery causing it to slightly raise the battery up and push up on the cover.
now his battery cover is really snug and actually takes a decent amount of effort to get off.
i was going to post pics but i think this is simple enough for people to figure out.
hope this helps those complaining about the loose/easy to get off door.