Whenever I try to open doors the icon for opening does not appear every time I put my center to the door. So at some point I lose some seconds when trying to escape some zombies by running through a house....
Also crawling through doors is not going very fluently, I get stuck many times.
Doors can be opened from first floor and through walls when not seeing them but pointing towards them within a certain distance.
After expierencing this I also noticed zombies running through walls and being 1/2 above floor and 1/2 inside the floor.