In Phobos there is a collision error. On the lift that goes to the snipping tower there is an edge, step, on the wall. If the player activates the lift and stands at the corner, they'll hit their heads and prevent the lift from going up. To solve this there should have been an invisible wall or the step should have been removed to prevent the player from hitting their heads there.

In CTF-Orbital there are these corridors with pillars on the walls. The collision here isn't a huge problem because the corridor is wide and most of the time players won't be running or jumping near the corridor's walls.

In DM-Grinder there is this circular hallway with pillars and low height girders that all hinder the player's movements. If the player runs sideways or jumps, hits the level's geometry and this split second could mean death.

Image credits: Gamer Max Channel

Many games have problems with unwanted collision. Places that shouldn't disallow the player from walking there have invisible walls. This is most often caused by the mismatch between one person making the art and another person making the collision. A game shouldn't have invisible walls that mislead the player. The windows in the screenshot are wide enough for the player to pass, yet they have invisible walls to prevent that. There is no glass so why block the player with an invisible wall?

In the middle of the road there is an invisible collision for no reason. The enemy died and dropped their weapon where the player is never going to reach. Why did they place an invisible collision there? No one will ever know.