There is an issue about this, please see https://github.com/mdjnelson/moodle-mod_customcert/issues/264.
Note - I no longer work for Moodle and have moved on (after 10 years of Moodle development!), so forgive my slowness.
Note - I no longer work for Moodle and have moved on (after 10 years of Moodle development!), so forgive my slowness.