diff --git a/src/navigator_data_ingest/base/api_client.py b/src/navigator_data_ingest/base/api_client.py
index c11bfad..a2a2c85 100644
--- a/src/navigator_data_ingest/base/api_client.py
+++ b/src/navigator_data_ingest/base/api_client.py
@@ -139,13 +139,21 @@ def upload_document(
 def _download_from_source(
     session: requests.Session, source_url: str
 ) -> requests.Response:
+    # Try the orginal source url
     download_response = session.get(source_url, allow_redirects=True, timeout=5)
 
     # TODO this is a hack and we should handle source urls upstream in the backend
     if download_response.status_code == 404:
-        download_response_altered = session.get(source_url.replace("%", ""), allow_redirects=True, timeout=5)
-        if download_response_altered.status_code == 200:
-            download_response = download_response_altered
+        # mutation 1 - remove %
+        download_response = session.get(
+            source_url.replace("%", ""), allow_redirects=True, timeout=5
+        )
+
+    if download_response.status_code == 404:
+        # mutation 2 - replace % with the encoded version, i.e. %25
+        download_response = session.get(
+            source_url.replace("%", "%25"), allow_redirects=True, timeout=5
+        )
 
     if download_response.status_code >= 300:
         raise Exception(