Zombie pigmen stays aggressive forever if they continuously respawn

I created a pigmen farm in the nether to test pigmen's new cooldown feature but it seem that this feature is broken again in 1.14.4. I hit a pigmen and they all started to attack me as normal. After five minutes they were still agressive so I decided to leave my computer open for the night and the next morning, they were still agressive toward me. Aside from that I got 131 levels of Xp