Imports create multiple attributes using same slug

Two separate attribute names (used for products in Woocommerce) have been designated the same slug. This was the result of two separate product imports using WP All Import.

Unfortunately this is in a production environment and the problem has not occured on the development server. I cannot disable theme or other plugins and experiment with imports.

In case it’s related to escaping characters I mention the attributes, one has an apostrophe (ATTRIBUTE NAME -> SLUG):

Payne’s gray -> paynes-gray
Paynes gray -> paynes-gray

(For the curious, Payne’s gray is a pigment mix.)

I believe the first row was imported first. The effect is that variant products belonging to the second attribute cannot be displayed. The system interprets them as out of stock.

I thought perhaps this was a WP bug at first, allowing for this behavior, but they recommended me posting here.