When a user has an item selected in their inventory during dimension change, the item will be dropped before the user teleports. This should not happen, because it leads to item loss.

This can be solved by:
1. saving the selected item in inventory on dimension change,
2. closing the inventory before the teleport (not recommended, because if the item is selected while the inventory is full, it will be dropped).

I noticed this bug even in earlier versions of Minecraft, but do not know exactly which versions are affected by it.

Video:
https://www.youtube.com/watch?v=ClU8dI2OyPI&feature=youtu.be