Apparently Duffy can walk through locked doors

If you meet Duffy outside the house (you may have to take the chance and not sit down in the wooden chair when Linder asks you to), you can get this:

>WEST
(hallway)
This is the south end of a hallway that runs the length of the house. At the far
end, to the north, you can see the living room; immediately to the south is a
door. Other doors on both sides lead to other rooms.
To the north Mr. Phong enters the hallway from the west.

>UNLOCK GARAGE DOOR
Okeh, the garage door is now unlocked.
Mr. Phong walks past you.

>OPEN GARAGE DOOR
Okeh, the garage door is now open.
Mr. Phong heads off to the east.

>SOUTH
(garage)
The garage, like a car port, has no door to keep the cars in. Doors lead north
and east. The walls are decorated with spare tires and things. Oil spots on the
floor show that a car is often parked here. The other car is a dark blue Bentley
3.5-liter sedan.
To the west Sgt. Duffy, with someone in tow, comes into view from the south.
Your assistant, Sgt. Duffy, sees you. "Detective, I'm glad you're safe! I
thought I should come here on the streetcar, in case you needed help. I'm
familiar with the house, since I was here to help investigate Mrs. Linder's
death. Just as I walked up tonight, I heard a shot! The next thing I knew, this
man, who calls himself Stiles, burst out of the woods behind the house.
Naturally, I put the nippers on him and brought him along. I'll just stow him in
the living room and stand by to help you."

>WEST
(driveway)
The driveway, paved with peastone, runs from the entrance at the south end in a
curve to a two-car garage at the east end. North of you is the front porch, the
entrance to the house.
Sgt. Duffy is leading Stiles by the handcuffs.
Sgt. Duffy leads Stiles off to the north.

>NORTH
(front porch)
The front porch is in an alcove, sheltered from the weather by the walls and
overhanging roof. A yellowish electric light hangs near the closed front door to
the east, giving you a dim view of the driveway to the south and the front yard
behind a gate to the north.
The gate is closed. A door bell glows at you, almost daring you to ring it.
Sgt. Duffy is leading Stiles by the handcuffs.
Sgt. Duffy leads Stiles off to the east.

>EAST
Too bad, but the front door is closed.

Phong didn't let him in, because he stayed in the office.

I think what happens is that usually, Stiles walks to FRONT-PORCH. When he reaches that, you will hear the door bell ring and Phong will start moving towards ENTRY. See I-STILES. But now, we met with Duffy before Stiles reached that goal, and so I-MEET-DUFFY? set LIVING-ROOM as his new goal.

It looks like MOVE-PERSON has a modification compared to Deadline so that actors walking will only open doors that aren't locked. But I guess they will still walk through them, leaving them closed and locked.

Phong will leave the office later, so this bug doesn't seem to break anything. It might not be worth fixing, but I just thought it was funny.

the-infocom-files / witness

Apparently Duffy can walk through locked doors #27