Challenges not tracking

This challenge is completely bugged, it's not counting explosive multi kills except for the occasional 1 once in a while. I've tried every explosive, tried targeting full vehicles and got multiple full tank kills with an RPG, yet nothing. gotten at least 6, triple kills with C4, yet only 3 of them have tracked, and of those 3, they were in Portal Bot lobbies. I also went and completed the 5 by 5 achievement with the HE launcher, and none of those counted either. I've yet to have one track in a regular multiplayer lobby or even consistently.