I was trying to diagnose why my icicle lights were not working. When plugged into a normal outlet, the first 3 bulbs were very dim almost unnoticeable . To test if current was getting all the way to the end I plugged in a spare strand to the female end of the icicle strand. The icicle strand lit up beautifully but the 2nd strand did not at all. I took apart the female end and didnt see anything wrong. What could cause this?