diff --git a/hawkbit-sdk/hawkbit-sdk-device/src/main/java/org/eclipse/hawkbit/sdk/device/DdiController.java b/hawkbit-sdk/hawkbit-sdk-device/src/main/java/org/eclipse/hawkbit/sdk/device/DdiController.java
index 9401519da..0aad284df 100644
--- a/hawkbit-sdk/hawkbit-sdk-device/src/main/java/org/eclipse/hawkbit/sdk/device/DdiController.java
+++ b/hawkbit-sdk/hawkbit-sdk-device/src/main/java/org/eclipse/hawkbit/sdk/device/DdiController.java
@@ -105,7 +105,7 @@ public class DdiController {
 
     public void stop() {
         if (executorService != null) {
-            executorService.shutdown();
+            executorService.shutdownNow();
         }
         executorService = null;
         lastActionId = null;
@@ -113,6 +113,7 @@ public class DdiController {
     }
 
     private void poll() {
+        log.debug(LOG_PREFIX + " Polling ...", tenantId, controllerId);
         Optional.ofNullable(executorService).ifPresent(executor ->
             getControllerBase().ifPresentOrElse(
                     controllerBase -> {