Ok new comment:
I was shooting my shotgun when I ran out of ammo, so i swaped to mt AK. Once the enemie was defeated i swapped back to the shotgun. For some reason it was stuck in its reload animation even though the ammo capacity was at full. You can still shoot but its kinda wierd. Right after that I got ambushed by 3 soldiers that had spawned without a warning. Thats not the problem though. The problem is, that they walked through walls.
As a fellow unity user i have 1 suggestion i can give you:
Try double checking the box colliders and rigid bodies on your enemies, and for the shotgun animation, I would open your animation manager and check your code to make sure it activates at the right time.
Keep it up!!! :D