Zombies have the same “nav hitbox” height regardless of type: crawlers will have the same height as normal ones and will not be able to crawl even where it’s visually and physically possible
Example: i made the custom object and confused the windows height (2 instead of 2.75), and zombies can’t walk through it (it’s easy to fix tho but the same problem can arise in places where it’s intended that it’s impossible to crawl through to full height (pipes, vents, basements, etc.))
(by the way, the same applies to the collision with the player)