in 1.16 java me and my friend were playing around with pvp so we would go into creative get our stuff and enchant it so i thought i would try something so i had a stick and i sneaked or crouched to activate 1 shield my main hand was holding a stick i used my mouse wheel to scroll to the next item which was a shield like i said 2 shields right clicked so that one was activated and then the both of them were activated that is not the point 

the thing that happened next was you know how if you use an axe and you hit a shield the shield gets disabled for a few seconds that did not happen i just sat there with my shields he was spamming his mouse buttons nothing would get past the shields axe trident bow crossbow sword i just sat there we tried everything but if you just do that you cant take damage and there weapons break than you whip out an  axe and they cant do anything