If this is the same problem as I am having, I contacted Sony and the rep first got me to go through a full software repair etc and then said it was a hardware fault and I should send it in for repair - which could take several days - without a phone.
The problem I have is that every now and then when I plug my earphones in (have tried several earphones) the sound continues to play through the phone speaker - it will not come through the earphones.
As soon as I shutdown and restart the phone all is OK and sound will come through the earphone each time I plug them in. I can unplug and plug back in and it continues to work - until next time - which could be the same day or after several days. Once again, as soon as I reboot it starts working fine.
I have tried killing apps / services etc when it stops working but it makes to difference - the only way to fix is reboot - which clearly points to a software / firmware issue.
The Sony support rep I spoke to just could not understand this concept and insisted it must be a hardware issue - she could not grasp that rebooting a phone does not fix a hardware issue!!
