Specifically, Microsoft says the new update may be an issue when you try connecting a Bluetooth speaker to a system that has an internal speaker. The specific update in question is update 4505903 on Windows 10 version 1903.

Once you’ve installed the update, there’s a chance that your Bluetooth speaker will not connect at all. And If it does, it may produce worse quality sounds than usual, or they will simply be produced by your system’s internal speaker instead. The solution to this, according to Microsoft, is to run the System File Checker tool (SFC.exe). To do this, you’ll have to run the command prompt with administrative authority, then type “sfc /scannow”. The process takes a few minutes, and will require a restart when it’s done. (Source: Microsoft via Windows Latest)

Windows 10 Update May Cause Problems With Bluetooth Speakers - 86