diff --git a/lib/taskana-core/src/main/java/pro/taskana/task/api/TaskService.java b/lib/taskana-core/src/main/java/pro/taskana/task/api/TaskService.java
index 60090b74d..af39a662a 100644
--- a/lib/taskana-core/src/main/java/pro/taskana/task/api/TaskService.java
+++ b/lib/taskana-core/src/main/java/pro/taskana/task/api/TaskService.java
@@ -330,15 +330,11 @@ public interface TaskService {
    *
    * @param taskQuery the task query.
    * @return the task that got selected and claimed
-   * @throws TaskNotFoundException if the task with taskId was not found
-   * @throws InvalidStateException if the state of the task with taskId is not READY
-   * @throws InvalidOwnerException if the task with taskId is claimed by someone else
-   * @throws NotAuthorizedException if the current user has no read permission for the
-   *     workbasket the task is in
+   * @throws InvalidOwnerException if the task is claimed by someone else
+   * @throws NotAuthorizedException if the current user has no read permission for the workbasket
+   *     the task is in
    */
-  Task selectAndClaim(TaskQuery taskQuery)
-      throws TaskNotFoundException, NotAuthorizedException, InvalidStateException,
-          InvalidOwnerException;
+  Task selectAndClaim(TaskQuery taskQuery) throws NotAuthorizedException, InvalidOwnerException;
 
   /**
    * Deletes a list of tasks.
diff --git a/lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskQueryImpl.java b/lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskQueryImpl.java
index 4381d8cbd..f90afde63 100644
--- a/lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskQueryImpl.java
+++ b/lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskQueryImpl.java
@@ -1110,6 +1110,8 @@ public class TaskQueryImpl implements TaskQuery {
     }
   }
 
+  // optimized query for db2 can't be used for now in case of selectAndClaim because of temporary
+  // tables and the "for update" clause clashing in db2
   public String getLinkToMapperScript() {
     if (DB.DB2.dbProductId.equals(getDatabaseId()) && !selectAndClaim) {
       return LINK_TO_MAPPER_DB2;
diff --git a/lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskServiceImpl.java b/lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskServiceImpl.java
index 985fd2b07..442074ec6 100644
--- a/lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskServiceImpl.java
+++ b/lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskServiceImpl.java
@@ -479,8 +479,7 @@ public class TaskServiceImpl implements TaskService {
 
   @Override
   public Task selectAndClaim(TaskQuery taskQuery)
-      throws TaskNotFoundException, NotAuthorizedException, InvalidStateException,
-          InvalidOwnerException {
+      throws NotAuthorizedException, InvalidOwnerException {
 
     if (LOGGER.isDebugEnabled()) {
       LOGGER.debug("entry to selectAndClaim(taskQuery = {})", taskQuery);
@@ -502,6 +501,8 @@ public class TaskServiceImpl implements TaskService {
 
       return claim(taskSummary.getId());
 
+    } catch (InvalidStateException | TaskNotFoundException e) {
+      throw new SystemException("Caught exception ", e);
     } finally {
       LOGGER.debug("exit from selectAndClaim()");
       taskanaEngine.returnConnection();
diff --git a/lib/taskana-core/src/test/java/acceptance/task/SelectAndClaimTaskAccTest.java b/lib/taskana-core/src/test/java/acceptance/task/SelectAndClaimTaskAccTest.java
index 01324d32a..9f065d506 100644
--- a/lib/taskana-core/src/test/java/acceptance/task/SelectAndClaimTaskAccTest.java
+++ b/lib/taskana-core/src/test/java/acceptance/task/SelectAndClaimTaskAccTest.java
@@ -50,14 +50,14 @@ class SelectAndClaimTaskAccTest extends AbstractAccTest {
       threads[i].join();
     }
 
-    assertThat(selectedAndClaimedTasks.stream().map(Task::getId))
+    assertThat(selectedAndClaimedTasks).extracting(Task::getId)
         .containsExactlyInAnyOrder(
             "TKI:000000000000000000000000000000000003",
             "TKI:000000000000000000000000000000000004",
             "TKI:000000000000000000000000000000000005",
             "TKI:000000000000000000000000000000000006");
 
-    assertThat(selectedAndClaimedTasks.stream().map(Task::getOwner))
+    assertThat(selectedAndClaimedTasks).extracting(Task::getOwner)
         .containsExactlyInAnyOrder("admin", "taskadmin", "teamlead-1", "teamlead-2");
   }
 
diff --git a/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/TaskController.java b/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/TaskController.java
index 116d4c5e7..d72909593 100644
--- a/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/TaskController.java
+++ b/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/TaskController.java
@@ -439,7 +439,7 @@ public class TaskController extends AbstractPagingController {
       params.remove(EXTERNAL_ID);
     }
 
-    for (int i = 1; i < 17; i++) {
+    for (int i = 1; i <= 16; i++) {
       if (params.containsKey(CUSTOM + i)) {
         String[] customValues = extractCommaSeparatedFields(params.get(CUSTOM + i));
         taskQuery.customAttributeIn(String.valueOf(i), customValues);