Steps to Reproduce:
1. Go to a block where there is a closed vertical trap door, and another one on the upper block.
2. Open the bottom trap door then the upper.
3. You do not crawl
You can also see the attached screenshots.
MC-248922
Crawling cannot be activated if the player's lower half intersects a non-full block
Open
1
(Unassigned)
Confirmed
Gameplay
Low
Player
1.18.2, 1.19.2, 1.20.2, 23w41a, 1.21.1, 24w36a
Retrieved
In order to crawl, you must not already be obstructed in the feet, and have enough space. The lower causes not enough space for crawling, but will prevent going into crawling as it obstructs the area. The same can be seen with dropping blocks onto you, you won't enter crawling if the block space is obstructed.