5mW-Laser not working on DRS

Weapon: DRS (LMG-class)
Top-Mount: 5mW-Laser (Green)

The 5mW-Laser is currently not working on the DRS, other lasers (red, blue) work fine. 
When the 5mW-Laser is attached, it is visible on the rifle and in-game (see Customization and Inspection), however there is no laser beam (see Ingame). 
Also the benefits (improved hipfire and smaller crosshair) are not present. 
The button to switch the laser on/off (standard "T") is not displayed above the ammo counter (also see Ingame). 

The game does not recognize the laser as attachment, although it is visible on the rifle.