If you are sneaking on top of a block and walk into bamboo that has a gap big enough to fit a player, you will fall off. However, the bug seems to only occur in certain situations.

Steps to Reproduce:

  1. Create a setup where you have a block, like dirt, next to bamboo. The bamboo needs to be on the far end from the block, so that there is a hole big enough to fit a player. The bamboo also needs to be taller than the block.
  2. Stand on top of the block and sneak.
  3. Walk towards the bamboo.

Observed Results:

You will fall off the block.

Expected Results:

You wouldn't fall off the block.

Notes:

The bug does not seem to occur if you are standing on bamboo, as in MC-160723. The bug also doesn't seem to occur if the bamboo is level with the block. The bug also seems to be present in Bedrock (MCPE-64930). Also, make sure that the gap between the block and the bamboo is the right size (see: no_gap.mp4). I have confirmed the bug on both 1.17.1 and 1.18 pre-release 5.