diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ExamDAO.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ExamDAO.java
index 5578eb0a..79a11977 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ExamDAO.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/ExamDAO.java
@@ -79,7 +79,7 @@ public interface ExamDAO extends ActivatableEntityDAO<Exam, Exam>, BulkActionSup
     @CacheEvict(
             cacheNames = ExamSessionCacheService.CACHE_NAME_RUNNING_EXAM,
             key = "#examId")
-    String getAppSigantureKeySalt(Long examId);
+    String getAppSignatureKeySalt(Long examId);
 
     /** Saves the Exam and updates the running exam cache. */
     @Override
@@ -171,7 +171,6 @@ public interface ExamDAO extends ActivatableEntityDAO<Exam, Exam>, BulkActionSup
 
     /** Use this to check if the exam is up to date
      *
-     * @param examId the exam identifier
      * @param exam the exam to check if it is in sync with the persistent or if there is a newer version
      * @return Result refer to the up-to-date result or to an error if happened */
     Result<Boolean> upToDate(Exam exam);
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/AdditionalAttributesDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/AdditionalAttributesDAOImpl.java
index 4fbdbc65..5004c810 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/AdditionalAttributesDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/AdditionalAttributesDAOImpl.java
@@ -154,6 +154,7 @@ public class AdditionalAttributesDAOImpl implements AdditionalAttributesDAO {
                 return this.additionalAttributeRecordMapper
                         .selectByPrimaryKey(rec.getId());
             } else {
+
                 final AdditionalAttributeRecord rec = new AdditionalAttributeRecord(
                         null,
                         type.name(),
@@ -170,6 +171,7 @@ public class AdditionalAttributesDAOImpl implements AdditionalAttributesDAO {
     }
 
     @Override
+    @Transactional
     public boolean initAdditionalAttribute(
             final EntityType type,
             final Long entityId,
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/ExamDAOImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/ExamDAOImpl.java
index cf4148cd..b0e6807a 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/ExamDAOImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/dao/impl/ExamDAOImpl.java
@@ -497,7 +497,7 @@ public class ExamDAOImpl implements ExamDAO {
     }
 
     @Override
-    public String getAppSigantureKeySalt(final Long examId) {
+    public synchronized String getAppSignatureKeySalt(final Long examId) {
         final CharSequence salt = KeyGenerators.string().generateKey();
         this.additionalAttributesDAO.initAdditionalAttribute(
                 EntityType.EXAM,
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/ExamSessionServiceImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/ExamSessionServiceImpl.java
index 0a257429..591622e8 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/ExamSessionServiceImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/ExamSessionServiceImpl.java
@@ -143,7 +143,7 @@ public class ExamSessionServiceImpl implements ExamSessionService {
                         return salt;
                     }
 
-                    return this.examDAO.getAppSigantureKeySalt(examId);
+                    return this.examDAO.getAppSignatureKeySalt(examId);
                 });
     }
 
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/SEBClientPingBlockingService.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/SEBClientPingBlockingService.java
index 471f8928..50045221 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/SEBClientPingBlockingService.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/SEBClientPingBlockingService.java
@@ -59,7 +59,7 @@ public class SEBClientPingBlockingService implements SEBClientPingService {
             log.error("Failed to get ClientConnectionDataInternal for: {}", connectionToken);
         }
 
-        if (instructionConfirm != StringUtils.EMPTY) {
+        if (StringUtils.isNotBlank(instructionConfirm)) {
             this.sebClientInstructionService.confirmInstructionDone(connectionToken, instructionConfirm);
         }