QC35ii noise/audio muffled at low volume
I have two pairs of Bose QC35ii: both with firmware version 4.5.2 and both manufactured in May 2019. When I listen to any audio over bluetooth with ANC off and turn down the volume, I clearly hear static-like noise that muffles the audio. The same issue is present in the near-silence between the songs. It is present on a wide range of hardware: Android (10, Pixel XL), Mac OS X (10.15.4, MacBook Pro), and Windows 10 (1909). The problem goes away on a wired connection with ANC off. (If ANC is on, the ANC-related hum makes it impossible to tell if the noise is there.) Is there a way to fix this? Thanks!