Baby Zombies stop attacking once in a while, and when the player is still

When baby zombies are chasing and attacking players and villagers, they sometimes stop for a second and look somewhere else, and continue attacking after 1 second.

They also completely stop attacking the player, if he keeps standing still. See the video clip attachment.

How to reproduce: This consistently happens every time they manage to hit the player, and they freeze if the player keeps standing still