Player switches output from PC back to phone after BT headset phone call

[mehist]

For some reason, if I have Spotify open in my phone and PC (music playing on the latter), it keeps switching audio output back to phone from PC after I take a phonecall with my BT headset. Any ideas as to why it keeps doing so?

Environment:

PC: Lenovo X1 Carbon on Windows 10

Phone: Sony E5603 on Android 6.0 with Bellboy BT headset

[rangleyourangle]

I am having the same problem with my Mac and iphone 7.  Music plays on desktop client.  After a phone call it immediately starts playing from the phone.  This only started happening in the last couple of weeks.