Maybe you didn't image copy the floppies correctly, if you're sure you image copied them and NOT copied them try switching the files (fdimaging MFSroot.flp into the previous kern.flp and vice versa) cause I faced the same problem with FreeBSD and it didn't load kern.flp except when I've done that

Another precaution is that if the FreeBSD files are on the same drive of the computer you're installing FreeBSD on it remember that when FreeBSD changes the filesystem of the drive it reformats it so the needed files will be deleted ..