Too many BT signals on can cause issues, not just w/Echo. You need to turn of BT signals on your phones when not using them; you can't just leave them on constantly in the house and paired with say, the Echo..
I just told Alexa to turn off Bluetooth. She replied, "There aren't any devices connected. You can un-pair your Bluetooth on your mobile device. So, try that, and un-pair your BT from phone with Echo. You can re-pair when needed.