I had this problem, I have the Atheros AR9485. It seems that you have to enable bluetooth coexistence manually. In this website https://wireless.wiki.kernel.org/en/users/drivers/ath9k/btcoex It says that the bluetooth card is AR3012. The only way I solved it was doing (I added this to a systemd sleep script)
modprobe -r ath9k && modprobe -r ath3k && modprobe ath9k btcoex_enable=1 && modprobe ath3k 