Steam Achievement Nice Work Dawg! doesnt' count

Hi,
I want to inform that the achievement Nice Work Dawg! “Earn a total of 2,500 Assist medals in multiplayer.” is currently bugged.
I play the PC version and tried Halo 3 (never worked), Halo 2:A, Halo 4 and Reach. My counter is stuck at 2366.

Kind regards.