I just caught a bit flip in a tmpfs. The 42 MiB file only existed for about 3 minutes before the error was first detected by the FLAC decoder. Very unlikely.

$ xxd -b ../08.\ New\ World\ Rising.flac >old
$ xxd -b 08.\ New\ World\ Rising.flac >new
$ diff old new
2959577c2959577
< 010ef510: 11110011 01001010 11111010 10011111 11110011 00111011  .J...;
---
> 010ef510: 11110011 11001010 11111010 10011111 11110011 00111011  .....;