Duplicate Choice Values in Dropdown Multi-Select Control

I have a control that filters records according to a text field - no extra computations in looker.

We would expect to be shown a list of unique instances of this field. But

I’m being shown duplicates of several entries in the field.I’m having a difficult time replicating this bug, and I don’t have authority to share the report, unfortunately.May I ask for leads or ideas as to why this problem happens? I use google sheets to consolidate records to link to looker studio. The built-in filters in google sheets don’t have this duplicate filter option problem.