You dont need to stack every single crate. I moved the nearest ones to the stacking zone. There are plenty in the incinerator room nearby.

I don't know how to share a screenshot in here so I will just explain it for an easy example: go in Quarantine room in the far-right corner (further to the right of the locked door) or alternatively, go in Ghost mode and look at the corners of some rooms from the outside, they can be seen easily.

With stacking and everything? How? Am I missing something?

I am aware of the crates and barrels being stuck in the shelves. I have moved some of them but not all of them. I haven't seen any tiny holes in the corners, you will have to send me a screenshot.

Also I to answer your previous comment, It is possible to complete the map in 2 hours. I have done it myself.

Some crates and barrels in shelves are too big and get stuck. Also, there's tiny holes in the corners of some walls

There's no way you can complete this map in 2-3 hours in singleplayer.