Yeah I second that,
I saw:
PHP Warning: Parameter 2 to bp_replace_members_filter() expected to be a reference, value given in snip.../wp-includes/plugin.php on line 166, referer: snip.../members/
so duly went and removed the ampersand and, hey presto, filtering sort of works as long as I use a select box rather than a multi select box.
Trouble is, I don’t know if there are any other side effects to this change.
Also, the plugin author suggests that this is not the place for such discussions, so hopefully the discussion will continue over here:
https://buddypress.org/community/groups/third-party-components-plugins/forum/topic/bp-member-filter/