User List Not Giving Correct Results When Searching Quickly

Steps to Repro:

1. Log into demo-test
2. Search users for "ar" (without quotation marks) - type quickly
3. View results (37 results - enough to fill the results page with a scrollbar visible)
4. NOTE: Result list doesn't seem right. Seems like it might be finding matches just for "a"?
5. Use scrollbar to scroll down

Expected: Should scroll down and scrollbar should remain visibile and results should be correct

Actual: Scrollbar disappears and I only see 5 records (these seem to be the correct search results, actually)

Screencast: https://www.screencast.com/t/vepbZ0F4