So I noticed this bug some time ago, but  I didn't bother checking it out because I thought it would be patched in another version of the game, but that didn't happen, so here I am. I noticed that after going thru a portal, either nether or end, the armor bars above your health bar disappears, although the armor is still equipped. The equipped armor does however not work. This has an easy fix, you just need to reequip the armor. This bug also affects elytras. I hope this bug gets patched soon, as going to the end with no armor is a real bad idea.