In some areas it as impssible to leave some bushes, objects etc. or it is very hard to leave.

Examples:

1. After leaving the plant in start of part 3, there is a harbour building where you can climb some stairs to get to the secound floor. There is a box in front of an broken/missing window.

When you jump down you will land in some bushes, a tree and a wooden box. I was not able to leave that bushes. I had to reload.

2. There is an improvised tent in the area with the train cars (before entering Turlip). I entered that tent (with a matress and some other stuff). It was hard to get out there.

3. Same area: there are some containers with a computer in it. If you enter the upper container, unlock the door with a key you will find a room with computers and a shower curtain.
I jumped upwards in front of the server in the back part of that small room and got caught within a cable which goes from left to right in that room at the ceiling. It took me quite a wile (hitting the D button) to move pixel by pixel. Finally I could leave the room.