Some reddit users reported that there were some problems in the audio system of the PC after updating kb4556799. Windows 10 reset all audio drivers, and even deleted Realtek audio drivers. Users say their audio devices will no longer be able to sound after the update is installed. However, this problem can be solved by disabling audio enhancements and reinstalling the Realtek driver.
In addition to audio problems, users of Microsoft forum reported that they had data loss problems after updating win10. It is worth noting that Microsoft may overwrite the default user profile when loading a temporary profile during the update process, which has been reported in the past. But Microsoft never acknowledged the problem.
One solution is to restart the PC about six to eight times to load the default profile and restore all user files. If the workaround does not fix the problem, users can also go to Settings > updates and Security > View update history > uninstall updates, and then uninstall the latest cumulative updates. When finished, return to update settings and pause the update to ensure that the problematic update is not downloaded again.