It should now be randomly disabled for a 3rd of Gehennom, to make things
a tad more interesting there. It's also disabled in Baalzebub's lair,
to make things a little more interesting.
Still don't know why the beetle is disappearing.
Newsgroup discussion has pointed out that after performing the
invocation ritual to gain access to the bottom level, it is possible to
skip almost all of Moloch's Sanctum by level teleporting in (and back out
to retry if necessary) directly to the high priest's temple. This fix
doesn't prevent entering that level via teleport or make you end up at
the stairs, it just forces arrival to be on the right side so that you'll
need to slog through the morgue room and the big chamber surrounding the
temple. Since there isn't much before the morgue aside from a few small
rooms with a secret door or two, it's no longer a very worthwhile shortcut.
