Problem:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=255057

Solution:

• Download DVD ISO.
• # mdconfig -f FreeBSD-13.0-RELEASE-amd64-dvd1.iso
• # mount_cd9660 /dev/mdX /media
• copy contents to folder.
• remove any files you don't want - in my case, all 32 bit binaries. I only run 64 bit code.
• mkisofs to create a new ISO file.
• burn CD from this new, slightly smaller ISO file.

If you don't have mkisofs …

# pkg install cdrtools