How to replicate issue:

1. Create a case with a multiselect dropdown - data coming from a DataPage accepting a filter value from another field (cascading Multiselect).
2. The user selects any value in the Multiselect. It can be one or more items from the list.
3. Click Save for later.
4. The user again opens the assignment and updates the value of another dropdown that will update the source of the Multiselect.
5. User selects any value in the Multiselect.

Issue: The old values of the Multiselect will come back and gets appended in the Multiselect.