The stabbing animation isn't working.

The stabbing animation isn't working. I'm on PC. I'm trying to get dog tags, but it only hits with the knife, not removes dog tags. After the update, I noticed a drop in my KD. I don't know what's causing it, since I was positive with K/D in the last game 15 minutes before the update. I haven't seen any updates regarding this and would like an explanation. Thanks.