Windows 10: Microsoft Bluetooth A2dp Source (Error 52)

[German]Some users are facing issues with the Bluetooth A2dp profile. They are receiving an error message that Windows cannot verify the digital signature and the driver drops error code 52. In August 2019 a number of Windows 10 users seem to have been hit. Here is some information about the issue. 

The problem description

I encountered the problem (when writing the post a week ago) via the collection service here, the entries are from September 2019, but the better introduction is this Microsoft Answers forum thread, dated August 13, 2019, where the issue has already been discussed. Within the post the user writes:

Microsoft Bluetooth A2dp source (error code 52) Microsoft Bluetooth A2dp source not working properly. There is error message "Windows cannot verify the digital signature for the drivers required for this device. A recent hardware or software change might have installed a file that is signed incorrectly or damaged, or that might be malicious software from an unknown source. (Code 52)".

His Bluetooth A2dp source is not working properly and drops error code 52. The error message indicates that Windows cannot verify the digital signature required for the drivers. It is caused by a recent hardware or software change. In the linked MS Answers forum thread some affected persons confirmed this behavior. It affects different devices, from Surface Pro 4 to HP Omen systems. A de- and subsequent reinstallation of the Bluetooth drivers is unlikely to help. It seems as if an unsigned driver (possibly via auto-update) has broken the systems. 

Note: August 13, 2019 was a patchday, and Microsoft later confirmed that an update disabled Bluetooth connections. I mentioned this in the article Windows 10 V1903: Update KB4505903 breaks Bluetooth speaker connection.

What's A2dp?

The abbreviation a2dp stands for Advanced Audio Distribution Profile. This is a manufacturer-independent technology that allows stereo audio signals to be sent wirelessly via Bluetooth to an appropriate receiver. A distinction is made between sources (transmitter, source) and sinks (receiver, sink). The source can be a computer or a smartphone; a Bluetooth headset or loudspeaker set, for example, is used as a sink. In the above error pattern, the source in the form of the relevant profile on the Windows 10 computer throws the error.

Attempts to fix this error

In the linked MS Answers forum thread some affected persons confirmed this issue. It affects different devices, from Surface Pro 4 to HP Omen systems. A de-installation and subsequent reinstallation of the Bluetooth drivers is unlikely to help. There are two ways to repair or replace the unsigned driver file with Windows 10.

#1: Try troubleshooting Bluetooth issues

The simplest solution is to try Windows 10's built-in troubleshooting. To do this, open the Settings app from the Start menu and select the Update and Security – Troubleshoot categories. Then select the Bluetooth troubleshooter in the right part of the window and let it run. Maybe this fixes the error – in the forum thread linked above, some users have been successful with the troubleshooter.

#2: Perform a system file check

What you should try in any case, if the troubleshooting does not help, is to run a system file check.

1. To do this, open an administrative command prompt by choosing Run as administrator. 2. Enter the command sfc /scannow and run the check.

In best case this finds damaged files and repairs them. This at least solved the problem for one user (the signed driver was then written back). There are also users who were successful with a driver update.