At the Cranes control point, I could see through a wall into the substructure of the render wireframe. Basically the world was translucent and i could see the dirty underbelly of the game world for a couple of blocks. This happened in a second location, that I can't recall the exact location of. It was in Downtown east, in an alley, where I was on an upper location on a cargo container. Same effect. See through the wall into the space below the wireframe.

Also, in my jaunt through the Dark Zone after the DZ intro mission, When taking cover on Stairs (first at building immediately north of DZ Gate 01, my character fell through the stairs into the underworld. It happened again when climbing on a planter terrace in one of the land marks, don't recall which. Happened on the edge of the planter, just like the edge of the stairs. I had to log out and back in to get free. The "returning to the playable area" message appeared and when the timer expired, I was left in place. So that didn't work. Having this occur twice put me off the DZ.