I also have a Moto S9HD headset. Although I don't currently have CORE player installed on my present Rom, I had it installed before. I seem to recall, in Settings of Core player, there are multiple pages of settings. One of those pages had some assignments for bluetooth to use the built in drivers, or to enable headset control. Something of that nature. It said experimental, I believe. But, if you find those settings, it may be worth a try!!
Hope this helps and I agree the S9HD's rock!