diff --git a/devicehandlers/FixedSlotSequence.cpp b/devicehandlers/FixedSlotSequence.cpp
index 07439e5d..e3d955d1 100644
--- a/devicehandlers/FixedSlotSequence.cpp
+++ b/devicehandlers/FixedSlotSequence.cpp
@@ -7,14 +7,8 @@ FixedSlotSequence::FixedSlotSequence(uint32_t setLengthMs) :
 }
 
 FixedSlotSequence::~FixedSlotSequence() {
-	// This should call the destructor on each list entry.
+	// Call the destructor on each list entry.
 	slotList.clear();
-//	SlotListIter slotListIter = this->slotList.begin();
-//	//Iterate through slotList and delete all entries.
-//	while (slotListIter != this->slotList.end()) {
-//		delete (*slotIt);
-//		slotIt++;
-//	}
 }
 
 void FixedSlotSequence::executeAndAdvance() {
@@ -87,8 +81,11 @@ uint32_t FixedSlotSequence::getLengthMs() const {
 }
 
 ReturnValue_t FixedSlotSequence::checkSequence() const {
-	// Iterate through slotList and check successful creation.
-	// Checks if timing is ok (must be ascending) and if all handlers were found.
+	if(slotList.empty()) {
+		error << "Fixed Slot Sequence: Slot list is empty!" << std::endl;
+		return HasReturnvaluesIF::RETURN_FAILED;
+	}
+
 	auto slotIt = slotList.begin();
 	uint32_t count = 0;
 	uint32_t time = 0;
diff --git a/devicehandlers/FixedSlotSequence.h b/devicehandlers/FixedSlotSequence.h
index a198421f..2fd866ac 100644
--- a/devicehandlers/FixedSlotSequence.h
+++ b/devicehandlers/FixedSlotSequence.h
@@ -12,13 +12,19 @@ using SlotListIter = std::multiset<FixedSequenceSlot>::iterator;
 /**
  * @brief	This class is the representation of a Polling Sequence Table in software.
  *
- * @details	The FixedSlotSequence object maintains the dynamic execution of device handler objects.
- * 			The main idea is to create a list of device handlers, to announce all handlers to the
- * 			polling sequence and to maintain a list of polling slot objects. This slot list represents the
- * 			Polling Sequence Table in software. Each polling slot contains information to indicate when and
- * 			which device handler shall be executed within a given polling period.
- * 			The sequence is then executed by iterating through this slot list.
- * 			Handlers are invoking by calling a certain function stored in the handler list.
+ * @details
+ * The FixedSlotSequence object maintains the dynamic execution of
+ * device handler objects.
+ *
+ * The main idea is to create a list of device handlers, to announce all
+ * handlers to thepolling sequence and to maintain a list of
+ * polling slot objects. This slot list represents the Polling Sequence Table
+ * in software.
+ *
+ * Each polling slot contains information to indicate when and
+ * which device handler shall be executed within a given polling period.
+ * The sequence is then executed by iterating through this slot list.
+ * Handlers are invoking by calling a certain function stored in the handler list.
  */
 class FixedSlotSequence {
 public:
@@ -111,7 +117,13 @@ public:
 	 */
 	SlotListIter current;
 
-	virtual ReturnValue_t checkSequence() const;
+	/**
+	 * Iterate through slotList and check successful creation.
+	 * Checks if timing is ok (must be ascending) and if all handlers were found.
+	 * @return
+	 */
+	ReturnValue_t checkSequence() const;
+
 protected:
 
 	/**
diff --git a/osal/FreeRTOS/FixedTimeslotTask.cpp b/osal/FreeRTOS/FixedTimeslotTask.cpp
index b1c97420..f8f80db2 100644
--- a/osal/FreeRTOS/FixedTimeslotTask.cpp
+++ b/osal/FreeRTOS/FixedTimeslotTask.cpp
@@ -57,18 +57,19 @@ ReturnValue_t FixedTimeslotTask::startTask() {
 
 ReturnValue_t FixedTimeslotTask::addSlot(object_id_t componentId,
 		uint32_t slotTimeMs, int8_t executionStep) {
-	if (objectManager->get<ExecutableObjectIF>(componentId) != NULL) {
+
+	if (objectManager->get<ExecutableObjectIF>(componentId) != nullptr) {
 		if(slotTimeMs == 0) {
-			// TODO: FreeRTOS throws errors for zero values.
-			// maybe there is a better solution than this.
+			// FreeRTOS throws a sanity error for zero values, so we set
+			// the time to one millisecond.
 			slotTimeMs = 1;
 		}
 		pst.addSlot(componentId, slotTimeMs, executionStep, this);
 		return HasReturnvaluesIF::RETURN_OK;
 	}
 
-	error << "Component " << std::hex << componentId
-		  << " not found, not adding it to pst" << std::endl;
+	error << "Component " << std::hex << componentId <<
+			" not found, not adding it to pst" << std::endl;
 	return HasReturnvaluesIF::RETURN_FAILED;
 }
 
diff --git a/osal/linux/FixedTimeslotTask.cpp b/osal/linux/FixedTimeslotTask.cpp
index 99cbf818..29eb37e7 100644
--- a/osal/linux/FixedTimeslotTask.cpp
+++ b/osal/linux/FixedTimeslotTask.cpp
@@ -40,8 +40,14 @@ uint32_t FixedTimeslotTask::getPeriodMs() const {
 
 ReturnValue_t FixedTimeslotTask::addSlot(object_id_t componentId,
 		uint32_t slotTimeMs, int8_t executionStep) {
-	pst.addSlot(componentId, slotTimeMs, executionStep, this);
-	return HasReturnvaluesIF::RETURN_OK;
+	if (objectManager->get<ExecutableObjectIF>(componentId) != nullptr) {
+		pst.addSlot(componentId, slotTimeMs, executionStep, this);
+		return HasReturnvaluesIF::RETURN_OK;
+	}
+
+	error << "Component " << std::hex << componentId <<
+			" not found, not adding it to pst" << std::endl;
+	return HasReturnvaluesIF::RETURN_FAILED;
 }
 
 ReturnValue_t FixedTimeslotTask::checkSequence() const {
diff --git a/osal/rtems/PollingTask.cpp b/osal/rtems/PollingTask.cpp
index c2dc629b..03ba0951 100644
--- a/osal/rtems/PollingTask.cpp
+++ b/osal/rtems/PollingTask.cpp
@@ -66,10 +66,16 @@ ReturnValue_t PollingTask::startTask() {
 	}
 }
 
-ReturnValue_t PollingTask::addSlot(object_id_t componentId, uint32_t slotTimeMs,
-		int8_t executionStep) {
-	pst.addSlot(componentId, slotTimeMs, executionStep, this);
-	return HasReturnvaluesIF::RETURN_OK;
+ReturnValue_t PollingTask::addSlot(object_id_t componentId,
+		uint32_t slotTimeMs, int8_t executionStep) {
+	if (objectManager->get<ExecutableObjectIF>(componentId) != nullptr) {
+		pst.addSlot(componentId, slotTimeMs, executionStep, this);
+		return HasReturnvaluesIF::RETURN_OK;
+	}
+
+	error << "Component " << std::hex << componentId <<
+			" not found, not adding it to pst" << std::endl;
+	return HasReturnvaluesIF::RETURN_FAILED;
 }
 
 uint32_t PollingTask::getPeriodMs() const {
diff --git a/parameters/ParameterWrapper.cpp b/parameters/ParameterWrapper.cpp
index 8f661bb3..1dac7075 100644
--- a/parameters/ParameterWrapper.cpp
+++ b/parameters/ParameterWrapper.cpp
@@ -91,7 +91,7 @@ template<typename T>
 ReturnValue_t ParameterWrapper::serializeData(uint8_t** buffer, uint32_t* size,
 		const uint32_t max_size, bool bigEndian) const {
 	const T *element = (const T*) readonlyData;
-	ReturnValue_t result;
+	ReturnValue_t result = HasReturnvaluesIF::RETURN_OK;
 	uint16_t dataSize = columns * rows;
 	while (dataSize != 0) {
 		result = SerializeAdapter<T>::serialize(element, buffer, size, max_size,