Steps to reproduce:

1. Lot in as a teacher in a course where there are at least two categories with questions in the question bank.
2. Go to the 'Questions' page for any quiz without attempts (e.g. https://qa.moodledemo.net/mod/quiz/edit.php?cmid=1171)
3. Choose Add -> From question bank
4. Close the dialogue that opens.
5. Choose Add -> From question bank again.
6. Change the category (e.g. to 'pre-written examples'
7. Click 'Apply filters'

Expected result: the list of questions in the dialogue updates.

Actual result: nothing appears to happen.

Explanation: The first dialogue opened at Step 3 still exists, but is hidden, and that gets updated, not the other dialogue that you can see.