Mobs will freeze in place visually but still be moving around invisible to the players and can attack you from far away from where their body is frozen, in order to attack them you have to run to where their body is frozen and attack that. When they die, their XP and drops are left wherever the invisible mob was. This also happens with villagers visually freezing in place but still moving around invisible and using beds/work blocks. Occasionally villagers will teleport to beds after being frozen and then slide out of bed and hover in the air “sleeping”.  The same thing happens with animal mobs, they’ll freeze visually while still wandering around invisible. The only thing that seems to help is players sleeping, but that usually only unfreezes a few mobs while the rest remain frozen.