Can't see certain items or armor on LAN

When I play with my friend on LAN it looks like they are holding a different block.

He was holding a pickaxe, but it looked like nothing was in his hand.

He was also wearing armor but it didn't look like he was wearing any.

Steps to Reproduce:
1. Hold an item on LAN with another person present
2. Check to see if they see the item

Steps to Reproduce:
1. Put on armor on LAN with another person present
2. Check to see if they see the armor

In the picture he really has cobblestone in his hand and full iron armor.