diff --git a/forensics/ingest.py b/forensics/ingest.py
index 9cb462a..ca89cdb 100644
--- a/forensics/ingest.py
+++ b/forensics/ingest.py
@@ -321,6 +321,7 @@ def save_invalid_upload(
                 validation_error=error,
             )
             if fallback_group is not None:
+                audit_file.groups.add(fallback_group)
                 AuditGroup.objects.filter(id=fallback_group.id).update(updated_at=timezone.now())
             return IngestionResult(audit_file=audit_file, created=True)
     except IntegrityError:
diff --git a/forensics/tests.py b/forensics/tests.py
index ad24a2a..53da759 100644
--- a/forensics/tests.py
+++ b/forensics/tests.py
@@ -1094,6 +1094,29 @@ def test_invalid_jsonl_returns_400_and_saves_quarantined_upload(self):
         self.assertEqual(bad_event.raw_line, "{not-json}")
         self.assertIn("JSON", bad_event.validation_error)
 
+    def test_invalid_utf8_group_upload_links_file_to_fallback_group(self):
+        raw_token, _token = UploadToken.issue("ios test client")
+        dump_bytes = b"\xff\xfeinvalid marmot audit bytes"
+
+        response = self.client.post(
+            reverse("api-group-audit-log-upload", kwargs={"group_slug": "mobile-qa"}),
+            data=dump_bytes,
+            content_type="application/x-ndjson",
+            HTTP_AUTHORIZATION=f"Bearer {raw_token}",
+        )
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.json()["validation_status"], AuditFile.STATUS_INVALID)
+        self.assertEqual(response.json()["group"], "mobile-qa")
+        self.assertEqual(response.json()["groups"], ["mobile-qa"])
+
+        audit_file = AuditFile.objects.get()
+        fallback_group = AuditGroup.objects.get(slug="mobile-qa")
+        self.assertEqual(audit_file.validation_status, AuditFile.STATUS_INVALID)
+        self.assertEqual(audit_file.events.get().group, fallback_group)
+        self.assertEqual(groups_for_audit_file(audit_file), [fallback_group])
+        self.assertEqual(list(audit_files_for_group(fallback_group)), [audit_file])
+
     def test_invalid_utf8_upload_file_sha256_race_returns_existing_audit_file(self):
         # save_invalid_upload() does the same check-then-create on file_sha256
         # as the valid ingestion path. If a concurrent request inserts the same
@@ -2123,6 +2146,35 @@ def test_unexpected_ingest_error_quarantines_upload_not_500(self):
         # The raw upload text is preserved intact as evidence, not dropped.
         self.assertEqual(audit_file.raw_text, body)
 
+    def test_unexpected_ingest_error_group_upload_links_file_to_fallback_group(self):
+        from django.db import DataError
+
+        raw_token, _token = UploadToken.issue("ios test client")
+        body = representative_audit_log()
+
+        with mock.patch.object(
+            ingest_module, "create_events", side_effect=DataError("simulated bind overflow")
+        ):
+            response = self.client.post(
+                reverse("api-group-audit-log-upload", kwargs={"group_slug": "mobile-qa"}),
+                data=body,
+                content_type="application/x-ndjson",
+                HTTP_AUTHORIZATION=f"Bearer {raw_token}",
+            )
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.json()["validation_status"], AuditFile.STATUS_INVALID)
+        self.assertEqual(response.json()["group"], "mobile-qa")
+        self.assertEqual(response.json()["groups"], ["mobile-qa"])
+
+        audit_file = AuditFile.objects.get()
+        fallback_group = AuditGroup.objects.get(slug="mobile-qa")
+        self.assertEqual(audit_file.validation_status, AuditFile.STATUS_INVALID)
+        self.assertEqual(audit_file.raw_text, body)
+        self.assertEqual(audit_file.events.get().group, fallback_group)
+        self.assertEqual(groups_for_audit_file(audit_file), [fallback_group])
+        self.assertEqual(list(audit_files_for_group(fallback_group)), [audit_file])
+
     def test_all_supported_audit_kind_variants_are_normalized(self):
         raw_token, _token = UploadToken.issue("ios test client")
         cases = [