Skype sounds stops media player or other sound sources

You can try commenting out the following modules in /etc/pulse/default.pa

#load-module module-role-cork

If that does not help, you can try changing flat-volumes to no in /etc/pulse/daemon.conf.

flat-volumes = no

If that still does not work, you can manually unload the module:

$ pactl unload-module module-role-cork