Animals and Horses (even leaded Entities) Mysteriously disappear after reloading a world (not every time). If the Entitie is leashed it disappears, only leaving the other end that's tied to the fence post. it's more common for leashed entities to disappear than ones in pens, and no holes are present in said pens. Villagers also tend to disappear often (sorry I don't have any photos or videos of this happening)
Related issues
Comments

Thank you for your report!
We're tracking this issue in MCPE-21416, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki
-- I am a bot. This action was performed automatically! Please report any issues in Discord or Reddit