diff --git a/series4_ingest.py b/series4_ingest.py
index bc48c3b..51b374e 100644
--- a/series4_ingest.py
+++ b/series4_ingest.py
@@ -153,8 +153,16 @@ def scan_thordata(root: str) -> Dict[str, Dict[str, Any]]:
                 parsed = parse_mlg_filename(fname)
                 if not parsed:
                     continue
-                unit_id, ts = parsed
+
+                unit_id, _ = parsed  # keep unit_id only
                 full_path = os.path.join(unit_path, fname)
+
+                try:
+                    mtime = os.path.getmtime(full_path)
+                    ts = datetime.fromtimestamp(mtime)
+                except Exception:
+                    continue
+                    
                 current = unit_map.get(unit_id)
                 if current is None or ts > current["last_call"]:
                     unit_map[unit_id] = {