No extermination medal?

Games Halo 5: Guardians
1

http://youtu.be/ncM4TX0X9ik

Why didn’t I get the extermination medal? I wiped out the entire enemy team with an overkill.

2

The medal is bugged at the moment I hope 343i fix the medal soon

3

http://youtu.be/ncM4TX0X9ik

4

Op you took too long killing the team either way someone already spawned