There is a problem with default container.
I did a test. If we use the default container for phpBB Console commands are loaded only the first time (when the cache is generated). Once the cache was generated, are no longer loaded.
To test this, change line 38 of bin/phpbbcli.php to:
$phpbb_container = phpbb_create_default_container($phpbb_root_path, $phpEx);
We can't use a "safe mode" parameter because container is created before the console application start.