Steps to reproduce:

1 Navigate to https://school.moodledemo.net/user/index.php?id=27 and log in as manager
2 Under 'Filters', change the 'Select' dropdown to 'Keyword'.
3 Click in the text box that appears next to it and type 'Frog'.
4 Press Tab; 'Frog' appears as a tag.
5 Press Tab again; the X button in the Frog tag is now highlighted.
6 Press Return.

EXPECTED: The Frog tag should be deleted
ACTUAL: Focus moves somewhere else (not sure where) but nothing else happens; you can press Tab to get back to the X button, but it still doesn't delete. If you press up or down arrow (which can probably be used to switch between tags if there are multiple tags, but in this example do nothing) and then press Return it will delete at that point.