Do the hints for the final room of the Soultaker's Pit in Avernum 5 uniquely identify a solution?

In the Soultaker’s Pit in Avernum 5, the final room (after you beat the Soultaker) contains four “stands”, positioned at the northeast, northwest, southeast, and southwest corners of a pit. To raise the portcullises to the north and south, one must configure the orbs on the four stands correctly and then ring the gong.

Each stand can either have a red-sparkling orb, a blue-sparkling orb, a green-sparkling orb, a non-sparkling orb, or no orb at all.

To help the player determine the correct configuration of the orbs, there are hints scattered throughout the Soultaker’s Pit (located on the walls; some of them are barely visible because lighting items scarcely work in the basement, and the color scheme is terrible for visibility). As far as I can tell, there are six hints:

• At least one stand to the north has no orb.
• A western orb has red sparkles.
• There are no blue sparkles.
• A sparkling orb to the north is not red.
• No sparkles are the same color.
• Two orbs are sparkling on the diagonal.

Now, I didn’t want to sit here and muddle through this myself, so I wrote a constraint solver that gave me the following two solutions:

1. Northwest = no orb; Northeast = green orb; Southeast = no orb; Southwest = red orb
2. Northwest = no orb; Northeast = green orb; Southeast = non-sparkling orb; Southwest = red orb

And I should think that both of these solutions are compatible with the six hints. However, solution (1.) summons a banshee; only solution (2.) actually opens the portcullises.

Am I misinterpreting the hints? Or did I miss a seventh hint that eliminates (1.)? (Or are both solutions valid and the devs just didn’t notice (1.)?)