Only just saw your post sorry.. Does it have a gloss finish steerer? One batch of forks had a hard gloss finish that can lower wedge and stem grip. A bit of wet + dry is a fix if you know what you're doing, also use grip paste on the stem and wedge surfaces. Could worth checking the stem type too, some lightweight aftermarket stems could have less contact area, more cut out internally.
It doesn't look like the shiny fork there though, if that's the neon yellow 2015 Arkose 2. As said above check the wedge/bung fitting with a torque wrench. Carbon grip paste is good stuff, still won't hurt to use some.