
This issue might occur when the FLAC files contain an ID3 frame before the FLAC header. The ID3 frame contains metadata such as title and artist. The FLAC property handler assumed that all FLAC files started with the 4 byte start code fLaC and did not take into account the ID3 frame at the beginning of the file. Therefore, the ID3 frame would be overwritten without the start code fLaC rendering the file unplayable.If you have corrupt FLAC files due to this bug, Microsoft explains how you can fix these files over here.
The update is part of the KB5003214 update, an optional non-security patch with various improvements and fixes for Windows 10 version 2004 and newer.