Windows 10 V1903: Update KB4505903 breaks Bluetooth speaker connection

[German]Cumulative Update KB4505903, released July 26, 2019, breaks the connection to Bluetooth speakers. Microsoft has just confirmed this as a known issue.


Update KB4505903 for Windows 10 V1903

Cumulative Update KB4505903 was released on July 26, 2019 – after extensive tests with Windows insiders – for Windows 10 Version 1903 as well as for Windows Server Version 1903. It fixes a long list of bugs and raises the OS build to 18362.267.

The update was released accidently on 07/25/2019 by mistake and then on 07/26/2019  inally. Users already reported within my German blog a slow installation on this release – and some user has install issues. I had reported about this update in Windows 10 V1903 Update KB4505903 (07/26/2019). There you can also find the hint:

Addresses an issue that may reduce Bluetooth audio quality when using certain audio profiles for extended periods.

Microsoft has also improved the Bluetooth audio output, the update is supposed to improve the quality.

Problems connecting to Bluetooth speakers

On 23 August 2019, Microsoft published the support article 4518538 Bluetooth speakers don't work after update 4505903 is installed on Windows 10, version 1903, which deals with connection problems with Bluetooth speakers. After installing update 4505903 on Windows 10 version 1903, one of the following problems occurs if an internal speaker is installed:

  • A Bluetooth speaker can't connect to the computer.
  • A Bluetooth speaker can connect to the computer. However, the speaker output sounds noisy (bad quality).
  • A Bluetooth speaker can connect to the computer. However, the sound is generated by the internal speaker instead of the Bluetooth device.

Additionally, in Device Manager, you notice an entry under the Sound, video and game controllers node for Microsoft Bluetooth A2dp Source that shows a yellow exclamation mark icon.


A workaround should help

In its support article 4518538, Microsoft proposes a workaround in the form of system file system checking. Open an administrative command prompt and type sfc /scannow in its window (see also the relevant part in the blog post Check and repair Windows system files and component store). 

It may take some time for the system file system check to run, the progress is displayed in the Command Prompt window. Then restart Windows 10. Then the Bluetooth pairing error should be fixed.

Somehow Microsoft hasn't been so comfortable with Bluetooth connections. Here in the blog I have reported several times about BT problems caused by updates. Older Bluetooth devices were deactivated by an update in June 2019 for security reasons (see Windows 8–10: Update blocks Bluetooth pairing).

However, in order for the system file system check to run cleanly, the bug caused by the July 2019 Defender updates should be fixed (see notes in the articles linked below). Whether the required Defender update with the sfc fix has already been rolled out, I can't say exactly at the moment – the error does not occur with me. The colleagues at explain that the fix for Defender will only be rolled out 'in the coming weeks'.

Similar articles:
Windows 10 V1903 Update KB4505903 (07/26/2019)
Microsoft fixes the Windows Defender sfc bug (August 2019)
Microsoft confirms July 9, 2019 Updates breaks sfc in Windows
Windows: July 9, 2019 Updates breaks sfc
Check and repair Windows system files and component store
Windows 8–10: Update blocks Bluetooth pairing

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