I also had this problem after upgrading to 17.10 and solved it with commenting out load-module module-switch-on-connect in /etc/pulse/default.pa.
When upgrading to 18.04 I opt for replacing the /etc/pulse/default.pa so the setting is back, but I don't have this issue, so it's fixed for me in 18.04.
I also had this problem after upgrading to 17.10 and solved it with commenting out load-module module- switch- on-connect in /etc/pulse/ default. pa.
When upgrading to 18.04 I opt for replacing the /etc/pulse/ default. pa so the setting is back, but I don't have this issue, so it's fixed for me in 18.04.