Put the summary of the bug you're having here

What I expected to happen was...:
The donkey should not disappear when I dismount

What actually happened was...:
The donkey disappeared when I dismounted him.

Steps to Reproduce:
1. Get a donkey
2. Put a saddle
3. Put a chest on it (mine has one)

4. Dismount

5. I have to save and re-open the map in order to see the donkey again

I have to mention that this bug happens from time to time.