I have an eight light set strung around the monitor here. They're a childhood leftover. Sometimes they don't bubble. Of coarse a quick snap with the finger and they start goin' again. I remember having to do that even when they were new and I had to reach high up to the middle of the tree to do that. My question....why does a finger snap start the bubbling? Not all the bulbs, just (randomly) some of them? And what's that crystal looking stuff in there?