In Kali we encountered many failed "apt update" with a mirror that was
slow to update and it always failed due to invalid checksums on
"Contents-amd64.gz".
Looking more closely, I discovered that "ftpsync" was not really kept
up-to-date with other files that are listed in the Release file and that
should be updated in stage 2 instead of stage 1.
I noticed in particular that dep11/* should also be handled like we
do for "i18n/*". And we might want to do it also for MD5SUMS/SHA256SUMS
files of debian-installer... although updates there are not very frequent.
Thank you in advance!