Add new var (inMachineList) to see if the machine is in the list.

code/controllers/master_controller.dm

@@ -311,6 +311,7 @@ datum/controller/game_controller/proc/processMobs()
 			#endif
 
 			if(PROCESS_KILL == Machinery.process())
+				Machinery.inMachineList = 0
 				Machinery.removeAtProcessing()
 				continue
 

code/game/machinery/machinery.dm

@@ -114,6 +114,8 @@ Class Procs:
 	var/panel_open = 0
 	var/area/myArea
 
+	var/inMachineList = 1
+
 /obj/machinery/New()
 	addAtProcessing()
 	return ..()