Every once in awhile my A string slips out of the nut when I'm playing. I assumed it was probably me bending the string too far or something. It didn't happen often. Until last night. Over the course of a 4 hour gig it popped out 4 or 5 times. I have a new nut ordered from Rickenbacker, but I was just wondering what would cause this to start happening more frequently. The nut is not chipped or broken and there is nothing under the string. I haven't changed the way I play or anything. I can't figure out why it is all of a sudden happening this often.