Sometimes freebsd-update can't work because some DNS do not resolve domain with upcase chars.
Error I get:
# freebsd-update fetch
Looking up update.FreeBSD.org mirrors... 1 mirrors found.
Fetching public key from update1.FreeBSD.org... failed.
No mirrors remaining, giving up.
Edit /etc/freebsd-update.conf and change following line:
I know this is not exactly a FreeBSD problem, but it can prevent system updates on certain providers.
If ISP's filter on this, then I'm relative sure they break RFC's.
However, if the dialogs tells it brought you from update.FreeBSD.org to update1.FreeBSD.org, then it looks like DNS is working.
Maybe this 2017 case failed on a human DNS error or cached entry to an old target.
Going from update.FreeBSD.org to update1.FreeBSD.org indicates there was a CNAME involved. I doubt this still is done like that, which probably also improved this issue.
So in resume:
lower/upper seem to work fine, CNAME target may have failed.