In my fps playable scene I bump into an object I cannot see. When I turn on physics vizualisation I can see a huge box/cube there but I can NOT find it in the outliner hiearchy!
It is not visible in viewport or in any game mode.
Make sure that it isn’t a hidden object that is also invisible. Then, try moving your objects to different layers, one object at a time (or in batches of 5)
Check your physics panel on the object to see if its collision bounds are set to box. There might be a random lonely vertex floating about somewhere in your mesh causing the box to be larger than the object would appear to be. if it is set to box, try set it to other bounds (like convex-hull or triangle-mesh).