The bug

When the player sneaks off of the shorter side of an anvil towards an adjacent glass pane or iron bar, they will fall into the gap. This does not occur if the glass pane is not present.

How to reproduce

• Place an anvil
• Place glass panes or iron bars adjacent to the narrower side of the anvil, such that there is a gap that the player can barely fit into
  • The bug occurs when there is a pane 1 block above the anvil (at the level of the player's feet), or if that block is missing and there are panes at the same height and 2 blocks above
• Sneak and move towards the pane