Zombie pigmen stays hostile

Hello, i noticed a problem with zombie pigmen which is super annoying, i made a gold farm which in order to work i need to hit one zombie pigman so he get angry and call for help and when being away they are supposed to stop being angry i believe.

another example i accidentally hit a zombie pigman and he got angry now i cant go anywhere in the nether because every single pigman is angry AND they don't despawn after being 125+ blocks away from them.

please fix.

thanks!