Rollback of Intel Smart Sound Technology for Bluetooth Audio also worked for me. Root-cause is that windows somehow no longer manages to switch Bluetooth Codecs from A2DP to and from HSP and back for me when the microphone is needed (most likely due to incompatible driver versions). Interestingly, only the bluetooth audio driver was updated, so I presume some automated update scheduling was botched.
TLDR: Working versions of the two drivers on my machines were
- 10.29.0.9677 for Intel Smart Sound Technology for Digital Microphones
- 10.29.0.7687 for Intel Smart Sound Technology for Bluetooth Audio