There are other reports addressing issue however I thought I would try to make a more effective bug report so we can make it easier to confirm since the others are marked as "Unconfirmed" and "Awaiting Response." The ones I've found are MCPE-89340, MCPE-124782, MCPE-129522. These reports describe the issue in previous versions. I only added the current version since I cannot personally confirm previous versions. This issue may be related to MCPE-42058 since they are all movement related issues that happen at the edge of an old size world.

Steps to Reproduce:
1. Create a new world with "World Type" set to "Old"
2. Go within 16 blocks of 2 of the 4 world borders
3. Crouch and walk off of an edge of a block

Observed Results:
The player falls off the edge of the block

Expected Results:
The player is prevented from falling off the edge of the block