Hi @Humberto_Andres_Hida,
I am guessing the issue is that both the launch you have described will launch the stretch_drive node simultaneously, which would make either one of them fail because only one stretch_driver node could run at an instance. I would recommend you comment out the stretch_driver node inclusion code block in the navigation.launch or the stretch_detect_objects.launch file so that the stretch driver node is only launched once.