The function linkOrgIdentity() in Model/CoPetition.php invokes

$this->EnrolleeCoPerson->HistoryRecord->record()

with a first argument of $coPersonId but that variable is not defined anywhere in that function.

The failure is masked when running with debug level '0' because the Javascript orchestrating the enrollment flow in the browser just keeps going since but with debug level '2' the browser will show the error.