Refactor exam_take function to use a canonical list of questions for consistent indexing and improved error handling for question navigation

physics/views.py

@@ -198,11 +198,25 @@ def exam_take(request, pk: int, sk: int, cid: str| None = None, passcode: str| N
 
     cid_user_exam = exam.get_or_create_cid_user_exam(cid=cid, user_user=request.user)
 
-    question = exam.get_questions()[sk]
+    # Use a single, canonical list of questions for all indexing/navigation
+    # operations to avoid mismatches between different querysets or orderings.
+    questions = list(exam.get_questions())
 
-    exam_length = len(exam.exam_questions.all())
+    # Validate sk and select the current question
+    try:
+        sk = int(sk)
+    except Exception:
+        raise Http404("Invalid question index")
 
-    pos = exam.get_question_index(question)
+    if sk < 0 or sk >= len(questions):
+        raise Http404("Question not found in exam")
+
+    question = questions[sk]
+
+    exam_length = len(questions)
+
+    # Since we're using the canonical list, the positional index is sk.
+    pos = sk
 
     if cid is not None:
         answer = question.cid_user_answers.filter(cid=cid, exam=exam).first()