So its been in the game since initial release of the throwing knives and is extremely annoying.
When you kill mobs like skeletons or phantoms, there is some sort of dusty cloud in the air after their death, and this very cloud that stays in the world for few seconds completely absorbing throwing knifes, so if you try to kill few mobs on one line of sight in a row you wont achieve this as all your knives thrown would be absorbed by this dust cloud. It doesnt happen with sword slashes or any sort of shots. I've got no idea why its still a thing really after such a long time. And i highly doubt that its an intended feature.
Throwing Knives issue
The "Dust cloud" still has the collider of the entity, that's why yout hit it with the knives.
This along with your other recent threads are essentially all bug reports and should as such be filed in a ticket to support rather than posted on forums. That way they are reported through the proper channels and can be addressed as such. You can file bug reports here.
Dropping anchor.
6 / 4
