Hello, I have lighting with 5 lights. The last light has no bulb in it, but the 3rd one flick on and off randomly. It happens every so often. What could be wrong? Could there be a loose wire? Or could not having a bulb on the end have something to do with it? Please help

Sounds like the light socket is not contacting properly. Try moving the socket over a little on the track. Check for any corrosion in the track itself, or where the socket makes contact. Use emery or fine sandpaper to clean up the contact points. Hope this helps.