I've read up and experimented and hence have been able to narrow down the cause of the problem to /boot. I should mention that I have tested both install62.iso and bsd.rd+http for 6.2-stable and several snapshots, including the most recent one as of now.
So, I tried using /boot from 6.2-stable on several snapshots, the first being from 18th October and the last being the most recent one as of now. 6.2-stable and all of these snapshots can boot any kernel (bsd, bsd.rd, ...) in this case. I then tried using /boot from the most recent snapshot (which is identical to /boot from 18th October snapshot) on 6.2-stable and the snapshots. In all cases, the system rebooted before the specified kernel could be loaded. # diff /boot.62-stable /boot.most_recent_snapshot Binary files /boot.62-stable and /boot.most_recent_snapshot differ # ls -l /boot.* -rw-r--r-- 1 root wheel 83772 Oct 25 00:07 boot.62-stable -rw-r--r-- 1 root wheel 81804 Oct 25 00:01 boot.most_recent_snapshot Now, from what I can find on cvsweb, the only recent change to files relating to /boot was eight days ago to the Makefile in https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/sys/arch/amd64/ stand/boot/ Files in https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/sys/stand/boot/ haven't changed for four months or more. So, is the Makefile change the culprit or am I missing something? Any help is greatly appreciated.