HI all, Whenever I have noise cancelling mode on my headset, the right earcup just makes a high-pitched background noise, or it is working but significantly louder than the left earcup. Both wired and wireless. Works fine in ambient sound or NC off mode. Yes, I have tried everything ,latest firmware, re-pair, phone and PC device, reset the device. After several painful chats with Amazon (where I got them from) and SONY support, I took it to a repair centre in north England. That was two weeks ago - haven't heard of it since. I have seen that several other reported similar issues with the XM3 and XM4. They have the same chip inside - so clearly not something out of the blue.. SONY, this one needs a quick firmware update!