iMac 27", High Sierra. External headphones with mic (Bose QC25 if it matters). Everything works fine after system boots up.
Then after some time (can be ~day, can be longer) mic on the headset stops working. Levels on this mic become extremely low to the point where Skype test call won't record anything that I'm speaking. Different apps (Zoom Conference call, Skype) behave same.
Reboot fixes the issue. Disconnecting and connecting headphones - doesn't. Playing with configuration options (System / Sounds) doesn't do any good either.