despawning bug

What specific device are you using? This should go in the "Environment" field as mentioned on the Report Creation form.
Does the same issue occur on a local copy of the world?

Please also note that many mobs (passive, hostile) will despawn automatically if the player is too far away from them.

This report has been temporarily closed as Awaiting Response. It will automatically reopen when you comment with new information. Please be sure to provide all requested information. Reports that do not contain enough information may be closed as Incomplete.