Currently, Primo shows the items in the facets (e.g. the subjects facet) either sorted alphabetically or by the number of items.
However, it seems to order the items randomly when the number of items is identical for several different subject heading in the facet.
It would be beneficial to be able to configure a secondary sort option for these items (for example when using a multilingual subject heading system - to present the same subject in both language one after the other).