diff --git a/src/ATBAPP/DeviceControllerDiag.cpp b/src/ATBAPP/DeviceControllerDiag.cpp
index 70658fb..e90e434 100644
--- a/src/ATBAPP/DeviceControllerDiag.cpp
+++ b/src/ATBAPP/DeviceControllerDiag.cpp
@@ -113,8 +113,8 @@ void DeviceControllerDiag::private_startDiag()
         qCritical() << "DeviceControllerDiag::private_startDiag() interrupted!";
         DCMachineEvent E255Event = DCMachineEvent(DeviceController::State::E255);
         if (!this->previousMachineEventSet.contains(E255Event)) {
-            machineEventSet.insert(E255Event);
-            private_sendDiagEvent(E255Event, DeviceController::Action::SET);
+            this->private_setDiagEvent(DeviceController::State::E255);
+            this->private_sendDiagEvent(E255Event, DeviceController::Action::SET);
         }
         if (this->E255counter > 5) {
             this->restartCArun();
@@ -132,9 +132,9 @@ void DeviceControllerDiag::private_startDiag()
              * - diag is called again in ModeOOO wokeup()
              */
         }
-        this->diagRequestTimeoutTimer->stop();
-        this->isRequestRunning  = false;
-        this->flagInterruptDiag = false;
+
+        this->private_finishDiag(false);
+
         return;
     }
 
@@ -178,15 +178,16 @@ void DeviceControllerDiag::sys_superviseSystem()
         // send
         DCMachineEvent E255Event = DCMachineEvent(DeviceController::State::E255);
         if (!this->previousMachineEventSet.contains(E255Event)) {
-            machineEventSet.insert(E255Event);
-            private_sendDiagEvent(E255Event, DeviceController::Action::SET);
+            this->private_setDiagEvent(DeviceController::State::E255);
+            this->private_sendDiagEvent(E255Event, DeviceController::Action::SET);
         }
         if (this->E255counter > 5) { this->restartCArun(); }
                               else { this->E255counter++; }
+
         QTimer::singleShot(400, this, &DeviceControllerDiag::diagRequest);
-        this->diagRequestTimeoutTimer->stop();
-        this->isRequestRunning  = false;
-        this->flagInterruptDiag = false;
+
+        this->private_finishDiag(false);
+
         return;
     }
 
@@ -196,16 +197,14 @@ void DeviceControllerDiag::sys_superviseSystem()
         qCritical() << "DeviceControllerDiag::sys_superviseSystem() no valid data!";
         hw->dc_autoRequest(true);
 
-        DCMachineEvent E255Event = DCMachineEvent(DeviceController::State::M0254);
-        previousMachineEventSet.insert(E255Event);
-        private_sendDiagEvent(E255Event, DeviceController::Action::SET);
+        DCMachineEvent M0254Event = DCMachineEvent(DeviceController::State::M0254);
+        this->private_setDiagEvent(DeviceController::State::M0254);
+        this->private_sendDiagEvent(M0254Event, DeviceController::Action::SET);
 
         if (this->E255counter > 5) { this->restartCArun(); }
                               else { this->E255counter++; }
         QTimer::singleShot(400, this, &DeviceControllerDiag::diagRequest);
-        this->diagRequestTimeoutTimer->stop();
-        this->isRequestRunning  = false;
-        this->flagInterruptDiag = false;
+        this->private_finishDiag(false);
         return;
     }
 
@@ -477,7 +476,7 @@ void DeviceControllerDiag::sub_componentAssessment()
 
 
     // finish diag
-    this->private_finishDiag();
+    this->private_finishDiag(true);
 }
 
 /**
@@ -486,14 +485,20 @@ void DeviceControllerDiag::sub_componentAssessment()
  * Single point to finish a diag process:
  *  -
  */
-void DeviceControllerDiag::private_finishDiag()
+void DeviceControllerDiag::private_finishDiag(bool dataValid)
 {
     this->diagRequestTimeoutTimer->stop();
     this->isRequestRunning  = false;
     this->flagInterruptDiag = false;
 
-    this->previousMachineEventSet.unite(machineEventSet);      // add new elements from machineEventSet
-    this->previousMachineEventSet.intersect(machineEventSet);  // remove elements not in machineEventSet
+    // add new elements from machineEventSet
+    this->previousMachineEventSet.unite(machineEventSet);
+
+    if (dataValid) {
+        // remove elements not in machineEventSet
+        // ... only if data is valid
+        this->previousMachineEventSet.intersect(machineEventSet);
+    }
 
     if (this->isDiagBackgroundTask) {
         this->isDiagBackgroundTask = false;
diff --git a/src/ATBAPP/DeviceControllerDiag.h b/src/ATBAPP/DeviceControllerDiag.h
index a228960..a46224d 100644
--- a/src/ATBAPP/DeviceControllerDiag.h
+++ b/src/ATBAPP/DeviceControllerDiag.h
@@ -170,7 +170,7 @@ private slots:
     void private_setDiagEvent(DeviceController::State result);
     void private_sendDiagEvent(DCMachineEvent result, DeviceController::Action action);
 
-    void private_finishDiag();
+    void private_finishDiag(bool dataValid = false);
 
     void sys_superviseSystem();