The new enterable doors that were added with the newest exp. patch are just slightly too narrow, and prevent a player from going through them while standing upright. Crouching/crawling through the door does work however.
http://images.akamai.steamusercontent.com/ugc/96096290118323864/8AEF874DF4E6D6A61E74F9B3C611543C93D0D1AB/