I had searched for other reports regarding this issue but I couldn't find one on this behavior even though it seems like something that would have already of been reported, but a ravager's head will glitch out if it dies at the beginning of its attack.

To see the glitch in action, spawn a ravager and have it attack something like a villager or iron golem, then while its head is extending, kill it and see that while it's in its death animation, its head will spaz out like crazy for some reason. You can use the following command below to summon a ravager with 1 hp to make it easier to test this.

/summon minecraft:ravager ~ ~ ~ {Health:1,Attributes:[{Name:"generic.max_health",Base:1f}]}

This is also easier to see if wearing thorns armor but this may just be a duplicate ticket as I just can't seem to find anyone else reporting this bug.