diff --git a/webapp/src/DataTransferObject/Shadowing/SubmissionFile.php b/webapp/src/DataTransferObject/Shadowing/SubmissionFile.php
index fe3848acfb..79310190bd 100644
--- a/webapp/src/DataTransferObject/Shadowing/SubmissionFile.php
+++ b/webapp/src/DataTransferObject/Shadowing/SubmissionFile.php
@@ -7,5 +7,6 @@ class SubmissionFile
     public function __construct(
         public readonly string $href,
         public readonly ?string $mime,
+        public readonly ?string $filename,
     ) {}
 }
diff --git a/webapp/src/Service/ExternalContestSourceService.php b/webapp/src/Service/ExternalContestSourceService.php
index d6bf05c4df..bc53ca6aec 100644
--- a/webapp/src/Service/ExternalContestSourceService.php
+++ b/webapp/src/Service/ExternalContestSourceService.php
@@ -200,7 +200,7 @@ public function getApiVersion(): ?string
             throw new LogicException('The contest source is not valid');
         }
 
-        return $this->cachedApiInfoData->version;
+        return $this->cachedApiInfoData?->version;
     }
 
     public function getApiVersionUrl(): ?string
@@ -209,7 +209,7 @@ public function getApiVersionUrl(): ?string
             throw new LogicException('The contest source is not valid');
         }
 
-        return $this->cachedApiInfoData->versionUrl;
+        return $this->cachedApiInfoData?->versionUrl;
     }
 
     public function getApiProviderName(): ?string
@@ -218,7 +218,7 @@ public function getApiProviderName(): ?string
             throw new LogicException('The contest source is not valid');
         }
 
-        return $this->cachedApiInfoData->provider?->name ?? $this->cachedApiInfoData->name;
+        return $this->cachedApiInfoData?->provider?->name ?? $this->cachedApiInfoData?->name;
     }
 
     public function getApiProviderVersion(): ?string
@@ -227,7 +227,7 @@ public function getApiProviderVersion(): ?string
             throw new LogicException('The contest source is not valid');
         }
 
-        return $this->cachedApiInfoData->provider?->version ?? $this->cachedApiInfoData->domjudge?->version;
+        return $this->cachedApiInfoData?->provider?->version ?? $this->cachedApiInfoData?->domjudge?->version;
     }
 
     public function getApiProviderBuildDate(): ?string
@@ -236,7 +236,7 @@ public function getApiProviderBuildDate(): ?string
             throw new LogicException('The contest source is not valid');
         }
 
-        return $this->cachedApiInfoData->provider?->buildDate;
+        return $this->cachedApiInfoData?->provider?->buildDate;
     }
 
     public function getLoadingError(): string
@@ -1435,6 +1435,14 @@ protected function importSubmission(Event $event, EventData $data): void
                     $zipUrl = ($this->basePath ?? '') . $zipUrl;
                 }
 
+                if ($this->source->getType() === ExternalContestSource::TYPE_CONTEST_PACKAGE && $data->files[0]->filename) {
+                    $zipUrl = $this->source->getSource() . '/submissions/' . $data->id . '/' . $data->files[0]->filename;
+                    if (!file_exists($zipUrl)) {
+                        // Common case: submissions are in submissions/<id>.zip
+                        $zipUrl = $this->source->getSource() . '/submissions/' . $data->id . '.zip';
+                    }
+                }
+
                 $tmpdir = $this->dj->getDomjudgeTmpDir();
 
                 // Check if we have a local file.