This behavior may be related to search constraints that are set up on the dropdown’s choices source that compares two text values. An inconsistency can occur between the values that the database filters and the values that the Bubble engine filters, resulting in options being displayed when it’s actually an empty list.
Modifying the search constraint so that the text fields do not cause an inconsistency in how the database versus the Bubble engine filters should help resolve this behavior. For reference, when comparing text, Bubble uses the unicode values of the text to perform the comparison.