Sometimes when loading in to an area or after talking to an npc, WASD controls don't move your character, clicking somewhere to move fixes this. In the underworld, when you're controlling another character, there are ledges that can only be traversed by click movement, WASD doesn't let you go up or down them.
Near the office parking area, you can go far enough forward that your character disappears from view. Same thing can happen in the underground parking lot, and likely any other sufficiently large area with a fixed camera position.  

Click movement is the default movement, WASD is more like a hacked-in feature, and I can't get it to trigger jumps for the time-being. I think I can fix WASD getting stuck sometimes, though.

I'll add some invisible walls to a few bigger areas like the parking lot.