diff --git a/src/Entity/Base/AbstractStructuralDBElement.php b/src/Entity/Base/AbstractStructuralDBElement.php
index cbe2c7be..921826b0 100644
--- a/src/Entity/Base/AbstractStructuralDBElement.php
+++ b/src/Entity/Base/AbstractStructuralDBElement.php
@@ -282,6 +282,12 @@ abstract class AbstractStructuralDBElement extends AttachmentContainingDBElement
      */
     public function getSubelements(): iterable
     {
+        //If the parent is equal to this object, we would get an endless loop, so just return an empty array
+        //This is just a workaround, as validator should prevent this behaviour, before it gets written to the database
+        if ($this->parent === $this) {
+            return new ArrayCollection();
+        }
+
         return $this->children ?? new ArrayCollection();
     }
 
diff --git a/src/Repository/AbstractPartsContainingRepository.php b/src/Repository/AbstractPartsContainingRepository.php
index eab2c26c..1bf4c31c 100644
--- a/src/Repository/AbstractPartsContainingRepository.php
+++ b/src/Repository/AbstractPartsContainingRepository.php
@@ -27,6 +27,8 @@ use InvalidArgumentException;
 
 abstract class AbstractPartsContainingRepository extends StructuralDBElementRepository implements PartsContainingRepositoryInterface
 {
+    private const RECURSION_LIMIT = 50;
+
     /**
      * Returns all parts associated with this element.
      *
@@ -55,8 +57,17 @@ abstract class AbstractPartsContainingRepository extends StructuralDBElementRepo
     {
         $count = $this->getPartsCount($element);
 
+        //If the element is its own parent, we have a loop in the tree, so we stop here.
+        if ($element->getParent() === $element) {
+            return 0;
+        }
+
+        $n = 0;
         foreach ($element->getChildren() as $child) {
             $count += $this->getPartsCountRecursive($child);
+            if ($n++ > self::RECURSION_LIMIT) {
+                throw new \RuntimeException('Recursion limit reached!');
+            }
         }
 
         return $count;
diff --git a/tests/Entity/Base/AbstractStructuralDBElementTest.php b/tests/Entity/Base/AbstractStructuralDBElementTest.php
index 4b124053..9a4104e5 100644
--- a/tests/Entity/Base/AbstractStructuralDBElementTest.php
+++ b/tests/Entity/Base/AbstractStructuralDBElementTest.php
@@ -144,4 +144,15 @@ class AbstractStructuralDBElementTest extends TestCase
         $this->assertSame([$this->root, $this->child1], $this->child1->getPathArray());
         $this->assertSame([$this->root], $this->root->getPathArray());
     }
+
+    public function testGetSubelements(): void
+    {
+        $this->assertSame([$this->child1, $this->child2, $this->child3], $this->root->getSubelements()->toArray());
+        $this->assertSame([$this->child1_1, $this->child1_2], $this->child1->getSubelements()->toArray());
+        $this->assertSame([], $this->child1_1->getSubelements()->toArray());
+
+        //If a element is set as its own parent, it should not be returned as a subelement
+        $this->child1->setParent($this->child1);
+        $this->assertSame([], $this->child1->getSubelements()->toArray());
+    }
 }
diff --git a/translations/validators.de.xlf b/translations/validators.de.xlf
index abdd0886..47ee7322 100644
--- a/translations/validators.de.xlf
+++ b/translations/validators.de.xlf
@@ -173,7 +173,7 @@
       </notes>
       <segment state="translated">
         <source>validator.noneofitschild.self</source>
-        <target>Ein Element kann nicht sein eigenenes übergeordnetes Element sein.</target>
+        <target>Ein Element kann nicht sein eigenenes übergeordnetes Element sein!</target>
       </segment>
     </unit>
     <unit id="pr07aV4" name="validator.noneofitschild.children">
diff --git a/translations/validators.en.xlf b/translations/validators.en.xlf
index e639fa67..51549395 100644
--- a/translations/validators.en.xlf
+++ b/translations/validators.en.xlf
@@ -164,7 +164,7 @@
       </notes>
       <segment state="translated">
         <source>user.invalid_username</source>
-        <target>The username must contain only letters, numbers, underscores, dots, pluses or minuses.</target>
+        <target>The username must contain only letters, numbers, underscores, dots, pluses or minuses!</target>
       </segment>
     </unit>
     <unit id="lZvhKYu" name="validator.noneofitschild.self">
@@ -173,7 +173,7 @@
       </notes>
       <segment state="translated">
         <source>validator.noneofitschild.self</source>
-        <target>An element can not be its own parent.</target>
+        <target>An element can not be its own parent!</target>
       </segment>
     </unit>
     <unit id="pr07aV4" name="validator.noneofitschild.children">
@@ -182,7 +182,7 @@
       </notes>
       <segment state="translated">
         <source>validator.noneofitschild.children</source>
-        <target>You can not assign children element as parent (This would cause loops).</target>
+        <target>You can not assign children element as parent (This would cause loops)!</target>
       </segment>
     </unit>
     <unit id="ayNr6QK" name="validator.select_valid_category">