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.)?)

There was one more hint that you missed that lets you uniquely identify the one:

At least one orb to the South doesn't sparkle.