Unironically, some shell shocked runs are literally only so hard because the first place you gotta go to has a fucking rat tunnel you can't get around.
If you found a grenade, it used to be possible to blow open the bottom door and skip the tunnel altogether if you throw it just right.
I think on the harder difficulties they patched it so it only works on easy and below.
Rat RNG is typically what determines your success or failure once you play the game enough in my opinion.