JEXL cannot get selected values from DropDownMultiple field

We have this weird bug in the binding of our database publishing template where we cannot retrieve the selected items from a multi-select box. This field works fine with slot queries, just not in the binding JEXL expression value.

Binding Value: $rx.keyword.keywordChoices(“shalecategories”)

Rhythmyx Version 6.7.0 Build 200906P01 (3218)[RX-15876]
Field Name: shalecategory
Field Control Type: sys_DropDownMultiple
Field Choices: Uses keyword “shalecategories”