Summary: If you're holding crouch and you are moving at the edge downwards, you can likely fall off of the staircase. This bug was fixed in Java, but hasn't made the cut on Bedrock.

Steps to reproduce:

1. Make a big staircase with stairs (any kind will work, did it with polished blackstone)
2. Go to the top of the staircase
3. Hold the crouch button
4. Move downwards at the edge

What should've happened: You stay on the staircase

What did happened: You fall off of the staircase

Images: Find them at MC-2404. I'm unable to provide a Bedrock Image of the bug.