Earlier this week all files mirrored from ISC were suddenly deleted by the Funet FTP mirror. The GW FTP mirror of BIND (and BIND 9) is a bit more conservative, so it only reported the fact that all files appear to have been deleted from the ISC server.
I finally had some time today to look into it, and I guess ISC upgraded their FTP server software (or configuration). It now ignores the -R flag in directory listings (for recursive listing of all subdirectories). I “fixed” the problem by instructing the mirror software to iterate through all directories individually. It’s painful, but there is no other option (no /ls-lRat file on the server).
The mirror at Funet has already retrieved the deleted files again, so we are in good shape on that front.