I wiped the dir. and DL the file again (
https://download.calibre-ebook.com/b...-5.99.7.tar.xz, (sha256: cba789af28dc4cd097755e16e63ae5b3fc0d98254f9be2a9e2 c08a035658fb0a, space inside sha is added by this bb-editor and must be deleted), resulting dir, unpacked, is 382,483,553 bytes, but I still get the same error.
I tried to DL (as a zip) the git-branch qt6, same version and same error (resulting dir is 48,872,261 bytes).
Options -w and -g of calibre-debug give me the same exception.
Anyway, I'll use the 5.99.7 binaries, so it's not a problem for me, as far as it's ok for you.