My Local Multiplayer World converted to 19w08b, normal difficulty, survival. We are 2 ppl,  I host.

Issue:
Everytime my friend goes into the Nether the Pigman get angry even when they where neutral when we he left the Nether. They also don't stop being angry at him, ever. If I stay in the Nether alone after he was in they shortly switch aggro, but quickly return to normal (like usually). If keep the Nether loaded and he joins after that it's fine, but if we unload the Nether and return they are angry again. 
We have tried deleting his playerfile and then returning. It resolved it until I died(Lava, no Pigman involved) in the Nether.

They don't care about us attacking other hostile mobs.
Ghast attacks don't seem to be the trigger either.
They do suicide fall of a cliff close to us while angered, that doesn't affect their state of angry either.
Their anger seem to come in waves, they seem to loose interest and scatter until suddenly they all form a ball of angry again.
Switching to creative for a bit seems to also be a way to calm then if we are in the Nether.

More background Details:
We were playing Nether today, I jumped of a  4 block high took damage and suddenly the Pigman were angry. But they just grunted angrily but didn't actually attack me at all. My friend was approximately 200-300 blocks away in the Nether as well.  When he returned a good while later, the Pigman actually started to attack.

I died in the Nether. We got rid off all Pigman in the Overworld and returned, to fiend the Pigman as expected still angry. But they just would not stop being angry.

Pictures:
Attached are some pictures of my friend standing on the roof for more then 5min usually surrounded by Pigman the whole time(not hurting them). And one picture of them ignoring me.