"Find a member" feature not working properly when one of the first char shortcuts has been clicked before

1. Click https://www.phpbb.com/community/memberlist.php
2. Click "K" or https://www.phpbb.com/community/memberlist.php?first_char=k#memberlist
3. Click "find members" or https://www.phpbb.com/community/memberlist.php?mode=searchuser&first_char=k
4. Set "*" as username.

The result: search finds only usernames that begins with k.

In my opinion this is not working as it should. There's no any indication you are still searching usernames starting with k.