diff --git a/src/Controller/Backoffice/QuizController.php b/src/Controller/Backoffice/QuizController.php
index 12f9420..3d5c4b2 100644
--- a/src/Controller/Backoffice/QuizController.php
+++ b/src/Controller/Backoffice/QuizController.php
@@ -264,7 +264,7 @@ class QuizController extends AbstractController
             'candidate' => $candidate,
         ]);
 
-        if (!$quizCandidate) {
+        if (!$quizCandidate instanceof \Tvdt\Entity\QuizCandidate) {
             // Create new QuizCandidate if it doesn't exist (inactive by default when first toggling)
             $quizCandidate = new QuizCandidate($quiz, $candidate);
             $quizCandidate->active = false;
diff --git a/src/Entity/Answer.php b/src/Entity/Answer.php
index 8b3cc7b..f862b36 100644
--- a/src/Entity/Answer.php
+++ b/src/Entity/Answer.php
@@ -13,7 +13,7 @@ use Symfony\Component\Uid\Uuid;
 use Tvdt\Repository\AnswerRepository;
 
 #[ORM\Entity(repositoryClass: AnswerRepository::class)]
-class Answer
+class Answer implements \Stringable
 {
     #[ORM\Column(type: UuidType::NAME)]
     #[ORM\CustomIdGenerator(class: 'doctrine.uuid_generator')]
diff --git a/src/Entity/Question.php b/src/Entity/Question.php
index cb63479..ed8471b 100644
--- a/src/Entity/Question.php
+++ b/src/Entity/Question.php
@@ -13,7 +13,7 @@ use Symfony\Component\Uid\Uuid;
 use Tvdt\Repository\QuestionRepository;
 
 #[ORM\Entity(repositoryClass: QuestionRepository::class)]
-class Question
+class Question implements \Stringable
 {
     #[ORM\Column(type: UuidType::NAME)]
     #[ORM\CustomIdGenerator(class: 'doctrine.uuid_generator')]
diff --git a/src/Entity/Quiz.php b/src/Entity/Quiz.php
index f451bc5..e067d1c 100644
--- a/src/Entity/Quiz.php
+++ b/src/Entity/Quiz.php
@@ -135,6 +135,7 @@ class Quiz
                     if (!isset($candidateCounts[$candidateId])) {
                         $candidateCounts[$candidateId] = ['name' => $candidate->name, 'count' => 0];
                     }
+
                     ++$candidateCounts[$candidateId]['count'];
                 }
             }
@@ -154,9 +155,9 @@ class Quiz
                 }
             }
 
-            if (!empty($missing) || !empty($duplicates)) {
+            if ($missing !== [] || $duplicates !== []) {
                 $errors = [];
-                if (!empty($missing)) {
+                if ($missing !== []) {
                     // If all active candidates are missing, show a special message
                     if (\count($missing) === \count($activeCandidates)) {
                         $errors[] = 'No candidates assigned to this question';
@@ -164,7 +165,8 @@ class Quiz
                         $errors[] = 'Missing candidates: '.implode(', ', $missing);
                     }
                 }
-                if (!empty($duplicates)) {
+
+                if ($duplicates !== []) {
                     $errors[] = 'Duplicate candidates: '.implode(', ', $duplicates);
                 }