The Bug

If a player climbs an iron bar from a horizontal chain the player looses sprint, even though he hasn't collided anywhere.

Steps to reproduce

1. Turn off Auto-Jump and set Sprint to Hold for easier reproduction.
2. Get into a redstone ready world
3. Run the following exact commands:

   /tp @p 0.18 ~ 0 0 0
   /fill 0 ~ 5 0 ~ 20 iron_bars
   /setblock -1 ~ 5 minecraft:chain[axis=x]
   

4. Sprint straight forward without moving the camera
   → Notice that you lose the sprint once you climb onto the ironbars