diff --git a/CMakeLists.txt b/CMakeLists.txt
index d8ca812e..bfe3da84 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,14 +10,15 @@ set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 set(FSFW_ETL_LIB_MAJOR_VERSION 20 CACHE STRING
     "ETL library major version requirement"
 )
-set(FSFW_ETL_LIB_VERSION ${FSFW_ETL_LIB_MAJOR_VERSION}.27.2 CACHE STRING
+set(FSFW_ETL_LIB_VERSION ${FSFW_ETL_LIB_MAJOR_VERSION}.27.3 CACHE STRING
     "ETL library exact version requirement"
 )
+set(FSFW_ETL_LINK_TARGET etl::etl)
 
 set(FSFW_CATCH2_LIB_MAJOR_VERSION 3 CACHE STRING
     "Catch2 library major version requirement"
 )
-set(FSFW_CATCH2_LIB_VERSION v${FSFW_CATCH2_LIB_MAJOR_VERSION}.0.0-preview4 CACHE STRING
+set(FSFW_CATCH2_LIB_VERSION v${FSFW_CATCH2_LIB_MAJOR_VERSION}.0.0-preview5 CACHE STRING
     "Catch2 library exact version requirement"
 )
 
@@ -76,9 +77,7 @@ if(FSFW_BUILD_UNITTESTS)
             GIT_TAG        ${FSFW_CATCH2_LIB_VERSION}
         )
 
-        FetchContent_MakeAvailable(Catch2)
-        #fixes regression -preview4, to be confirmed in later releases
-        set_target_properties(Catch2 PROPERTIES DEBUG_POSTFIX "")
+        list(APPEND FSFW_FETCH_CONTENT_TARGETS Catch2)
     endif()
 
     set(FSFW_CONFIG_PATH tests/src/fsfw_tests/unit/testcfg)
@@ -123,7 +122,22 @@ if(NOT ${FSFW_ETL_LIB_NAME}_FOUND)
         GIT_TAG        ${FSFW_ETL_LIB_VERSION}
     )
 
-    FetchContent_MakeAvailable(etl)
+    list(APPEND FSFW_FETCH_CONTENT_TARGETS ${FSFW_ETL_LIB_NAME})
+endif()
+
+# The documentation for FetchContent recommends declaring all the dependencies
+# before making them available. We make all declared dependency available here
+# after their declaration
+if(FSFW_FETCH_CONTENT_TARGETS)
+    FetchContent_MakeAvailable(${FSFW_FETCH_CONTENT_TARGETS})
+    if(TARGET ${FSFW_ETL_LIB_NAME})
+        add_library(${FSFW_ETL_LINK_TARGET} ALIAS ${FSFW_ETL_LIB_NAME})
+    endif()
+    if(TARGET Catch2)
+        # Fixes regression -preview4, to be confirmed in later releases
+        # Related GitHub issue: https://github.com/catchorg/Catch2/issues/2417
+        set_target_properties(Catch2 PROPERTIES DEBUG_POSTFIX "")
+    endif()
 endif()
 
 set(FSFW_CORE_INC_PATH "inc")
@@ -387,7 +401,7 @@ target_compile_options(${LIB_FSFW_NAME} PRIVATE
 )
 
 target_link_libraries(${LIB_FSFW_NAME} PRIVATE
-    ${FSFW_ETL_LIB_NAME}
+    ${FSFW_ETL_LINK_TARGET}
     ${FSFW_ADDITIONAL_LINK_LIBS}
 )
 
diff --git a/automation/Dockerfile b/automation/Dockerfile
index 9df67fc8..0eb98fbb 100644
--- a/automation/Dockerfile
+++ b/automation/Dockerfile
@@ -6,3 +6,9 @@ RUN apt-get --yes upgrade
 #tzdata is a dependency, won't install otherwise
 ARG DEBIAN_FRONTEND=noninteractive
 RUN apt-get --yes install gcc g++ cmake make lcov git valgrind nano iputils-ping
+
+RUN git clone https://github.com/catchorg/Catch2.git && \
+	cd Catch2 && \
+	git checkout v3.0.0-preview5 && \
+	cmake -Bbuild -H. -DBUILD_TESTING=OFF && \
+	cmake --build build/ --target install
diff --git a/automation/Jenkinsfile b/automation/Jenkinsfile
index d1459e52..6abf5636 100644
--- a/automation/Jenkinsfile
+++ b/automation/Jenkinsfile
@@ -3,7 +3,7 @@ pipeline {
         BUILDDIR = 'build-tests'
     }
     agent {
-        docker { image 'fsfw-ci:d1'}
+        docker { image 'fsfw-ci:d2'}
     }
     stages {
         stage('Clean') {
diff --git a/src/fsfw/container/HybridIterator.h b/src/fsfw/container/HybridIterator.h
index e8b24a3d..ad000ec2 100644
--- a/src/fsfw/container/HybridIterator.h
+++ b/src/fsfw/container/HybridIterator.h
@@ -10,16 +10,23 @@ class HybridIterator : public LinkedElement<T>::Iterator, public ArrayList<T, co
   HybridIterator() {}
 
   HybridIterator(typename LinkedElement<T>::Iterator *iter)
-      : LinkedElement<T>::Iterator(*iter), value(iter->value), linked(true) {}
+      : LinkedElement<T>::Iterator(*iter), linked(true) {
+    if (iter != nullptr) {
+      value = iter->value;
+    }
+  }
 
-  HybridIterator(LinkedElement<T> *start)
-      : LinkedElement<T>::Iterator(start), value(start->value), linked(true) {}
+  HybridIterator(LinkedElement<T> *start) : LinkedElement<T>::Iterator(start), linked(true) {
+    if (start != nullptr) {
+      value = start->value;
+    }
+  }
 
   HybridIterator(typename ArrayList<T, count_t>::Iterator start,
                  typename ArrayList<T, count_t>::Iterator end)
       : ArrayList<T, count_t>::Iterator(start), value(start.value), linked(false), end(end.value) {
     if (value == this->end) {
-      value = NULL;
+      value = nullptr;
     }
   }
 
diff --git a/src/fsfw/globalfunctions/matching/MatchTree.h b/src/fsfw/globalfunctions/matching/MatchTree.h
index f7775d45..68b8f270 100644
--- a/src/fsfw/globalfunctions/matching/MatchTree.h
+++ b/src/fsfw/globalfunctions/matching/MatchTree.h
@@ -179,6 +179,9 @@ class MatchTree : public SerializeableMatcherIF<T>, public BinaryTree<Serializea
   virtual ReturnValue_t cleanUpElement(iterator position) { return HasReturnvaluesIF::RETURN_OK; }
 
   bool matchSubtree(iterator iter, T number) {
+    if (iter == nullptr) {
+      return false;
+    }
     bool isMatch = iter->match(number);
     if (isMatch) {
       if (iter.left() == this->end()) {
diff --git a/src/fsfw/subsystem/Subsystem.cpp b/src/fsfw/subsystem/Subsystem.cpp
index 4e9d52f3..27e6ae8e 100644
--- a/src/fsfw/subsystem/Subsystem.cpp
+++ b/src/fsfw/subsystem/Subsystem.cpp
@@ -30,11 +30,11 @@ ReturnValue_t Subsystem::checkSequence(HybridIterator<ModeListEntry> iter,
     return FALLBACK_SEQUENCE_DOES_NOT_EXIST;
   }
 
-  if (iter.value == NULL) {
+  if (iter.value == nullptr) {
     return NO_TARGET_TABLE;
   }
 
-  for (; iter.value != NULL; ++iter) {
+  for (; iter.value != nullptr; ++iter) {
     if (!existsModeTable(iter->getTableId())) {
       return TABLE_DOES_NOT_EXIST;
     } else {
@@ -66,13 +66,18 @@ HybridIterator<ModeListEntry> Subsystem::getCurrentTable() {
 void Subsystem::performChildOperation() {
   if (isInTransition) {
     if (commandsOutstanding <= 0) {  // all children of the current table were commanded and replied
-      if (currentSequenceIterator.value == NULL) {  // we're through with this sequence
+      if (currentSequenceIterator.value == nullptr) {  // we're through with this sequence
         if (checkStateAgainstTable(currentTargetTable, targetSubmode) == RETURN_OK) {
           setMode(targetMode, targetSubmode);
           isInTransition = false;
           return;
         } else {
-          transitionFailed(TARGET_TABLE_NOT_REACHED, getSequence(targetMode)->getTableId());
+          Mode_t tableId = 0;
+          auto seq = getSequence(targetMode);
+          if (seq.value != nullptr) {
+            tableId = seq->getTableId();
+          }
+          transitionFailed(TARGET_TABLE_NOT_REACHED, tableId);
           return;
         }
       }
@@ -248,10 +253,13 @@ ReturnValue_t Subsystem::handleCommandMessage(CommandMessage *message) {
     case ModeSequenceMessage::READ_TABLE: {
       ReturnValue_t result;
       Mode_t table = ModeSequenceMessage::getSequenceId(message);
-      EntryPointer *entry = NULL;
+      EntryPointer *entry = nullptr;
       result = modeTables.find(table, &entry);
-      if (result != RETURN_OK) {
+      if (result != RETURN_OK or entry == nullptr) {
         replyToCommand(result, 0);
+        if (entry == nullptr) {
+          return result;
+        }
       }
 
       SerializeIF *elements[2];
diff --git a/src/fsfw/subsystem/Subsystem.h b/src/fsfw/subsystem/Subsystem.h
index 84d5f6a7..4eae94bd 100644
--- a/src/fsfw/subsystem/Subsystem.h
+++ b/src/fsfw/subsystem/Subsystem.h
@@ -1,14 +1,13 @@
 #ifndef FSFW_SUBSYSTEM_SUBSYSTEM_H_
 #define FSFW_SUBSYSTEM_SUBSYSTEM_H_
 
-#include <FSFWConfig.h>
-
 #include "../container/FixedArrayList.h"
 #include "../container/FixedMap.h"
 #include "../container/HybridIterator.h"
 #include "../container/SinglyLinkedList.h"
 #include "../serialize/SerialArrayListAdapter.h"
 #include "SubsystemBase.h"
+#include "fsfw/FSFW.h"
 #include "modes/ModeDefinitions.h"
 
 struct TableSequenceBase {