The latest QuietComfort 35 firmware update has borked the headphones active noise cancelling (ANC) abilities, accord to widespread reports.

The issue was spotted soon after version 4.5.2 was released last month with many of the complaints being logged in the Bose community forums. One unhappy customer wrote that the new update had “severely lowered the quality of ANC” and that the noise cancelling function was nowhere near as effective as it used to be.
…
Read full post here:
https://www.trustedreviews.com/news/bose-qc35-firmware-noise-cancelling-3922813