In June I purchased the WF-1000XM4s as I was in the market for some wireless headphones and these came up as the best, over the past few weeks I've noticed a few problems, and I know I'm not alone in my findings. The problems for me are to do with the noise cancellation and ambient sound features, after a few hours of continuous use in noise cancellation or ambient sound mode, a hissing begins in the left earbud, this sound continually loudens until it becomes so distracting I'd rather use my £2 pair of wired earbuds. Even after resetting the earbuds -both individually and completely- the issue persists and when not connected to the phone or laptop, I also notice the same droning hissing sound in both earbuds immediately upon joining a phone call which makes me think it might be some hardware fault. Another issue I have is intermittent Bluetooth connection; often when listening on LDAC, the Bluetooth signal breaks up beyond comprehension although I'm certain this is just a limitation of the codec in a place such as my flat where a lot of interference occurs. Would love to know if I'm alone in the first issue and would like Sony to find out about this, really hoping a software update can fix these buds as they sound amazing!