diff --git a/src/Serializer/StructuralElementNormalizer.php b/src/Serializer/StructuralElementNormalizer.php
index 7ce774f9..bf3e1097 100644
--- a/src/Serializer/StructuralElementNormalizer.php
+++ b/src/Serializer/StructuralElementNormalizer.php
@@ -23,6 +23,7 @@ declare(strict_types=1);
 namespace App\Serializer;
 
 use App\Entity\Base\AbstractStructuralDBElement;
+use App\Serializer\APIPlatform\SkippableItemNormalizer;
 use Symfony\Component\DependencyInjection\Attribute\Autowire;
 use Symfony\Component\Serializer\Normalizer\NormalizerAwareInterface;
 use Symfony\Component\Serializer\Normalizer\NormalizerAwareTrait;
@@ -36,6 +37,8 @@ class StructuralElementNormalizer implements NormalizerInterface, NormalizerAwar
 {
     use NormalizerAwareTrait;
 
+    public const ALREADY_CALLED = 'STRUCTURAL_ELEMENT_NORMALIZER_ALREADY_CALLED';
+
     public function supportsNormalization($data, ?string $format = null, array $context = []): bool
     {
         //Only normalize if we are doing a file export operation
@@ -43,15 +46,25 @@ class StructuralElementNormalizer implements NormalizerInterface, NormalizerAwar
             return false;
         }
 
+        if (isset($context[self::ALREADY_CALLED]) && in_array($data, $context[self::ALREADY_CALLED], true)) {
+            //If we already handled this object, skip it
+            return false;
+        }
+
         return $data instanceof AbstractStructuralDBElement;
     }
 
-    public function normalize($object, ?string $format = null, array $context = []): \ArrayObject|bool|float|int|string
+    public function normalize($object, ?string $format = null, array $context = []): \ArrayObject|bool|float|int|string|array
     {
         if (!$object instanceof AbstractStructuralDBElement) {
             throw new \InvalidArgumentException('This normalizer only supports AbstractStructural objects!');
         }
 
+        //Avoid infinite recursion by checking if we already handled this object
+        $context[self::ALREADY_CALLED] = $context[self::ALREADY_CALLED] ?? [];
+        $context[SkippableItemNormalizer::DISABLE_ITEM_NORMALIZER] = true;
+        $context[self::ALREADY_CALLED][] = $object;
+
         $data = $this->normalizer->normalize($object, $format, $context);
 
         //If the data is not an array, we can't do anything with it
@@ -75,7 +88,8 @@ class StructuralElementNormalizer implements NormalizerInterface, NormalizerAwar
     public function getSupportedTypes(?string $format): array
     {
         return [
-            AbstractStructuralDBElement::class => true,
+            //We cannot cache the result, as it depends on the context
+            AbstractStructuralDBElement::class => false,
         ];
     }
 }
diff --git a/src/Services/InfoProviderSystem/Providers/Element14Provider.php b/src/Services/InfoProviderSystem/Providers/Element14Provider.php
index de51de46..91249156 100644
--- a/src/Services/InfoProviderSystem/Providers/Element14Provider.php
+++ b/src/Services/InfoProviderSystem/Providers/Element14Provider.php
@@ -46,7 +46,7 @@ class Element14Provider implements InfoProviderInterface
         'rohsPhthalatesCompliant', 'SVHC', 'tariffCode', 'usEccn', 'hazardCode'];
 
     private readonly HttpClientInterface $element14Client;
-    
+
     public function __construct(HttpClientInterface $element14Client, private readonly Element14Settings $settings)
     {
         /* We use the mozilla CA from the composer ca bundle directly, as some debian systems seems to have problems
@@ -77,7 +77,7 @@ class Element14Provider implements InfoProviderInterface
 
     public function isActive(): bool
     {
-        return trim($this->settings->apiKey) !== '';
+        return $this->settings->apiKey !== null && trim($this->settings->apiKey) !== '';
     }
 
     /**
@@ -308,4 +308,4 @@ class Element14Provider implements InfoProviderInterface
             ProviderCapabilities::DATASHEET,
         ];
     }
-}
\ No newline at end of file
+}
diff --git a/src/Services/InfoProviderSystem/Providers/TMEClient.php b/src/Services/InfoProviderSystem/Providers/TMEClient.php
index df198717..ae2ab0d1 100644
--- a/src/Services/InfoProviderSystem/Providers/TMEClient.php
+++ b/src/Services/InfoProviderSystem/Providers/TMEClient.php
@@ -48,7 +48,7 @@ class TMEClient
 
     public function isUsable(): bool
     {
-        return !($this->settings->apiToken === '' || $this->settings->apiSecret === '');
+        return !($this->settings->apiToken === null || $this->settings->apiSecret === null);
     }
 
     /**
@@ -59,7 +59,7 @@ class TMEClient
     public function isUsingPrivateToken(): bool
     {
         //Private tokens are longer than anonymous ones (50 instead of 45 characters)
-        return strlen($this->settings->apiToken) > 45;
+        return strlen($this->settings->apiToken ?? '') > 45;
     }
 
     /**
@@ -94,4 +94,4 @@ class TMEClient
 
         return $params;
     }
-}
\ No newline at end of file
+}
diff --git a/tests/Serializer/StructuralElementNormalizerTest.php b/tests/Serializer/StructuralElementNormalizerTest.php
index b151f249..79f739fa 100644
--- a/tests/Serializer/StructuralElementNormalizerTest.php
+++ b/tests/Serializer/StructuralElementNormalizerTest.php
@@ -41,6 +41,9 @@ class StructuralElementNormalizerTest extends WebTestCase
         //Get an service instance.
         self::bootKernel();
         $this->service = self::getContainer()->get(StructuralElementNormalizer::class);
+        //Inject the serializer, as the normalizer as this is not handled by the DI container
+        $this->service->setNormalizer(self::getContainer()->get('serializer'));
+
     }
 
     public function testNormalize(): void
diff --git a/tests/Validator/Constraints/ValidGoogleAuthCodeValidatorTest.php b/tests/Validator/Constraints/ValidGoogleAuthCodeValidatorTest.php
index a1bc1a74..6eb9270e 100644
--- a/tests/Validator/Constraints/ValidGoogleAuthCodeValidatorTest.php
+++ b/tests/Validator/Constraints/ValidGoogleAuthCodeValidatorTest.php
@@ -87,7 +87,7 @@ class ValidGoogleAuthCodeValidatorTest extends ConstraintValidatorTestCase
                         return [];
                     }
 
-                    public function eraseCredentials()
+                    public function eraseCredentials(): void
                     {
                     }