Re: Firmware 4.5.2 QC35 ii
I've just registered to say there are others who are just following this thread @bose.
To help in some way, the headphones were updated via. ios app. I installed the desktop app to try the 'reset' steps posted, the desktop app stated I was on version ~2.0.1 and I should update to 4.5.2. It seems odd the desktop app detected a really old version when I already had 4.5.2 installed on the headphones. I have the AE version manufactured in 2017 if that makes a difference.
I use the headphones daily on the London Tube and the screeching is coming through louder. The background noise is coming through louder IMO. As you previously stated your tests are showing no changes, but I would suggest trying it on the Tube where the difference is day and night.