Alias needs to start with a letter. If the title starts with a number e.g. '10
years ...' GenerateAlias creates an alias that starts '10-years...'. I just did
the following but I suspect there are more elegant solutions :)

            if (empty($lise_item->alias)) {
                // if title starts with a number, add an 'a_'
                $alias = preg_replace('/^(\d)/', 'a_$1', $lise_item->title);
$lise_item->alias = api::GenerateAlias($alias,
$this->instance_name );
            }