ALL my mobs are despawning. I've had two NAMED axolotls despawn, 3 tamed, saddled, and leashed horses despawn, and 4 tamed wolves despawn. This isn't that annoying for me, but I am annoyed about the horses (they were pretty good). I can't really include a screenshot because the mobs are already gone, and it wouldn't be a picture of much (also I had over 50 chickens despawn, and mobs that are about 2 chunks away are despawning).
Related issues
Comments

This issue has already been reported. Duplicate MCPE-21416.
You can add additional information or just vote for the solution to this problem in the specified report.
@unknown problem about tridents MCPE-141539 🙂

Thank you for your report!
We're tracking this issue in MCPE-144208, 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! The ticket was resolved by one of our moderators, and I left this message to give more information to you.
this happened to me too. I had a goat in a boat for the achievement because I was waiting for the notification, thinking "how could I possibly mess this up?" I left only to come back and find the goat missing. My villagers fortunately have survived several recent updates and are still around, having no nametags.
Tridents thrown by the player will also despawn 😞