Sometimes in the nether, a nametagged piglin looks like it's despawn, but it isnt, you can even barter with it. It is just invisible. This also happened with some zombified piglin. I'm not sure when or why this happens, but when i leave the nether by a nether portal and I enter it again, it is like normal.
Summary:

-Nametagged mobs sometimes appear invisible, it only happened int the nether.

-Only happened to zombified piglins and regular piglins.

-Happens random, unable to reproduce.

-Leaving and entering nether solves the proplem temporarily.

This is it. Thanks for you help!
Ps; I don't speak English, so this is may have been written a bit weirdly or wrong, but I tried my best.