diff --git a/api.asp b/api.asp
index 380a52b..fba0c1e 100644
--- a/api.asp
+++ b/api.asp
@@ -1821,13 +1821,20 @@ Function CreatePCMachineRelationship(pcMachineid, machineNumber)
     ' previous PC's relationship is stale (PC was replaced). Soft-archive via
     ' isactive=0 keeps history but excludes from active inventory views (the
     ' display pages already filter on isactive=1).
+    '
+    ' Match the equipment on EITHER side of the row. Legacy prod data stores
+    ' some Controls links reversed (machineid = PC, related_machineid =
+    ' equipment) instead of the canonical Equipment -> PC shape this function
+    ' writes. A direction-blind archive catches both, so a self-registering
+    ' DSC asset cannot leave a stale legacy controller active alongside it.
+    ' The new PC's own link (either direction) is preserved by the <> guards.
     Dim archiveSQL
     archiveSQL = "UPDATE machinerelationships " & _
                  "SET isactive = 0, lastupdated = NOW() " & _
-                 "WHERE machineid = " & CLng(equipmentMachineid) & _
-                 "  AND related_machineid <> " & CLng(pcMachineid) & _
-                 "  AND relationshiptypeid = " & CLng(relationshiptypeid) & _
-                 "  AND isactive = 1"
+                 "WHERE relationshiptypeid = " & CLng(relationshiptypeid) & _
+                 "  AND isactive = 1" & _
+                 "  AND ( (machineid = " & CLng(equipmentMachineid) & " AND related_machineid <> " & CLng(pcMachineid) & ")" & _
+                 "     OR (related_machineid = " & CLng(equipmentMachineid) & " AND machineid <> " & CLng(pcMachineid) & ") )"
     LogToFile "CreatePCMachineRelationship: Archiving stale relationships: " & archiveSQL
     objConn.Execute archiveSQL
     If Err.Number <> 0 Then
@@ -2732,6 +2739,12 @@ Sub LogToFile(message)
 
     Set logFile = Nothing
     Set fso = Nothing
+
+    ' Logging is best-effort. A failed write (e.g. logs dir not writable) must
+    ' never leak Err into callers - several callers run under On Error Resume
+    ' Next and test Err.Number right after a LogToFile call, so a logging
+    ' failure would otherwise be misread as a fatal error.
+    Err.Clear
 End Sub
 
 ' ============================================================================