There are 4 events in /phpbb/attachment/delete.php and all they are broken.
core.delete_attachments_collect_data_before - var sql_id is undefined.
core.delete_attachments_from_database_after - all vars but $mode, $ids, $resync are undefined.
core.delete_attachments_before - all vars are undefined.
core.delete_attachments_from_filesystem_after - all vars but $space_removed, $files_removed are undefined.
It's old and looks like 3.1->3.2 code refactoring consequence.