I encountered a wall with some buggy collision/cover physics, located in an alley outside the ODEA Electronics bulding in the northwest corner of Downtown East, just north of the Fallen Cranes control point.
Taking cover against the wall positioned me on top of it instead, floating in mid-air. Leaving cover made me fall onto the floor, and certain positions also gave me the "outside playable area" warning timer.
In the distance further down the alley, some glitchy walls can also be seen disappearing and reappearing at certain viewing angles.
Video: https://www.youtube.com/watch?v=yDlZhh71WUk