When I had crafted a new shield, the item had damage. 170/180 uses.
Now i really wanted to try the new shield which works from blocking attacks, but, when taking damage it changes colour and name, sometimes completely mixing colour from name (view picture).
How i did this:
Summon/find a attacking mob
Block its front attack
Then the mob attacks, the shield changes colour and name or either one.
Thats this glitch summed up.