When trying to name capabilities of additional course reports added to course/report as coursereport/customreportname:view and expecting string being fetched within the plugin scope as course/report/customreportname/lang/xx_utf8/coursereport_customereportname.php, this strategy fails :

For this standard strategy to be solved :

add the folowing entry :

'coursereport_' => array('course/report'),

to the place list in places_to_search_for_lang_strings() (moodlelib.php)