The crouch_one_cm objectives stat does not work when you jump before sneaking.

How to reproduce :

Create the crouch_one_cm scoreboard with this command : 

/scoreboard objectives add crouch_one_cm minecraft.custom:minecraft.crouch_one_cm

Display this one in the sidebar :
/scoreboard objectives setdisplay sidebar crouch_one_cm

When you crouch, the value increases. But if you jump and before you fall back to the ground you crouch, the value doesn't increase even if you move.