If you hit a player wearing Thorns 3 diamond armor and you also have Thorns 3 diamond armor on, the game will crash on who created the world, not who joined the world.
For example player A has full diamond armor (each piece of armor is enchanted with thorns 3) and player B has the same armor. Player A created the world and Player B joined the world. Now Player A beats Player B and the game crashes on Player A. Also, if player B beats player A, player A's game crashes.

I have NOT tested this bug with other armor and other enchantment levels.
I testet this Bug on Windows 10 and Android 11