I've been having an issue with the Daredevil variant of the Elytrian class where it stops working after a bit. With that variant, you're supposed to be able to click the jump button mid-air to get a boost, but after a short while, it stops working until you die. Rejoining the world/server does not fix it.
As of now, I've been using the mod in the Euphoric Curiosity modpack, so it could be a conflicting mod, but I'll test the mod alone and update this if it turns out to be the mod itself. Otherwise, I'll try to identify the mod that's causing it and let everybody know here which one it is.
I'm using version 1.17-1.0.3.

Never mind. I just figured out that it's linked to hunger. It would be nice if that was stated though.