Recently file explorer has been having issues with the properties/metadata of FLAC files (Again!), this time the issue appears to be metadata corruption (artists, year, genre etc etc) caused cover arts with file sizes equal to or greater than 2^22 (4,194,304 bytes).
The tags are present before applying the cover art, but as soon as the image is applied to the FLAC file (Using MP3Tag v3.19) all of the metadata vanishes from file explorer and removing the cover art from the file doesn't make the information reappear again.
MP3Tag and media players such as VLC players still show the metadata perfectly, so I presume that the actual file data isn't corrupt itself, but possibly some sort of cached version of the info used by file explorer is corrupted instead which is unable to update.
First thing I did was make a 10,000 x 10,000 JPG and PNG of a solid colour in paint and apply them to a FLAC file, both formats worked and caused no issues.
Second thing I tried was to download different sized cover arts from the apple music website. The file name of the cover art on the website is actually a resolution size (e.g. 1500x1500bb.jpg) and changing this parameter to something like 9999x9999bb.jpg it lets you download the highest quality file that the source file can allow. Using this method of changing the image size I basically trial and errored different image resolutions which would result in different file sizes of the same picture and I narrowed the problem down to two images with only a single row and column of pixels difference in size with very close file sizes but the larger one causes the corruption issue.
The smaller image shows in windows as Size: 3.99MB (4,186,577 bytes) and Size on disk: 3.99MB (4,190,208 bytes).
The larger image shows in windows as Size: 3.99MB (4,191,240 bytes) and Size on disk 4.00MB (4,194,304 bytes).
First thing I assumed was that the file size exceeding 4MB is what caused the issue, but then the 4,194,304 looked familiar and that's because it's 2^22 which is a bit coincidental. I suspect something here might be related to the problem, maybe a mathematical issue in Windows' ability to read the cover art metadata if it's size meets or exceeds 4,194,304 bytes?
Purely speculation from someone that doesn't write software but that seems like a good guess to me.