Se cambiar tenancy_id por tenancyId en la petición de clientes.

Form/ChoiceList/Loader/ClientChoiceLoader.php

@@ -154,7 +154,7 @@ class ClientChoiceLoader implements ChoiceLoaderInterface
         $params = array();
         if ($filter !== false) {
             $params['name'] = urlencode($filter);
-            $params['tenancy_id'] = $this->tenancyService->getTenancyIdCurrent();
+            $params['tenancyId'] = $this->tenancyService->getTenancyIdCurrent();
         }
         $choices = $this->webservice->getChoices('client', $params);