Since when the N4 is not anymore supported, last month in OTA 13 the was a bug specifically solved for Mako. https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/1318360
Moreover, there is high likelihood the future fix for this bug https://bugs.launchpad.net/ubuntu/+source/ofono/+bug/1516696 would help to find this bug.
Regards
Since when the N4 is not anymore supported, last month in OTA 13 the was a bug specifically solved for Mako. https:/ /bugs.launchpad .net/ubuntu/ +source/ pulseaudio/ +bug/1318360
Moreover, there is high likelihood the future fix for this bug https:/ /bugs.launchpad .net/ubuntu/ +source/ ofono/+ bug/1516696 would help to find this bug.
Regards