Summary
In the latest version of the mod, when trying to crawl by holding down the hotkey, the player is lifted back up.

Running Environment

• Minecraft Version: Forge 1.20.1
• ParCool Version: 3.3.0.2
• Forge Version (optional): 47.3.12

Detail
I bound crawling to the V hotkey, and when the player holds the key, it lowers him to the ground for 1 tick, then lifts him up.

I tried to replicate it by binding crawl key to V key but the phenomenon didn't occur.
First please try to update your files to latest version.
Does this issue always occur when you try? Are you using other mods together?

I agree, first I checked on my modpack, and there this problem appeared with the latest update of the mod. Apparently this is a conflict with some of the other mods, but there are so many of them that I can't guess what exactly affected it. In a separate modpack, where there is only ParCool, the problem did not appear. I am attaching 2 videos, 1 - only with ParCool, 2 - on my modpack DarkTFC Ultrahardcore (it is published on Modrinth, so you can specifically download the latest version of the modpack and update ParCool manually to reproduce the bug)
1 - https://youtu.be/vmz582FVbhU
2 - https://youtu.be/TWGRS61vx0c