Melee Mobs of zombie/husk type stop attacking if you dont move.

Was testing some mobs I was making for my server through a plugin and noticed that the baby zombie would stop attacking me and just look at me for no reason. I loaded up 1.15.1 vanilla Minecraft single player redstone ready flat world with no other changes to see if it was plugins causing issue. The issue continues even in the vanilla game. I tested this on both zombies and husks in both adult and baby form. I have only seen this happen when I have only one mob attacking me at a time.

What was expected to happen?

Zombies and husks continue to attack and move toward me in an aggressive manner while aggroed to player right next to them.

What actually happen?

I had a single mob aggro me come into kill me hit me once or twice then stop and just look around. The babies stop attacking more easily than the adults as long as I do not move but both ages do it after a few seconds. They will eventually randomstroll away from me and then reaggro, come back to attack, then stop and look around after I have been hit a couple times without moveing (walking around, I can move point of view).

Steps to reproduce:
1. Start a new world on 1.15.1 in single player (originally found on paper spigot local host)
2. Find an open flat area
3. Spawn a single baby/adult (baby easier to reproduce) zombie/husk
4. Stand still and just look at mob actions until they stop attack (2 to 30 seconds)

Videos links of it happening
Baby Zombie
https://1drv.ms/v/s!AhCDtP1kfke5oze0_aujD-zYONT-?e=Z5Z9ju

Adult Husk perfect example at 35 seconds in

https://1drv.ms/v/s!AhCDtP1kfke5ozjJ-jpvkl5dciPd?e=tDYtrm