Default [Q] nexus 5 + custom rom - No full control of music over bluetooth to headunit

hi all,

i've got a nexus 5 thats connected to my car via bluetooth. i've noticed that its not sending full control of music over to the headunit.

The nexus has AOKP installed onto it and before another ROM which did the same thing.

My nexus 7 which is on a rooted stock rom works just fine and gives full control over to the head unit.

Is this a aftermarket rom issue or something else?

if it helps both devices were using google music to play