I thought I had an effective work around but it apparently only works for a limited number of drops per project. For the number of bumpers I use to break up a typical news show, I guess GarageBand’s code for mixing down the multiple tracks is just getting confused.
I will continue to do some research and experimentation throughout the week. Time to hit the Apple forums and see if anyone else is having the problem and has a better workaround. There are also some other things I did not try that I will experiment with the last show’s audio, see if I can reduce or eliminate the annoying glitches.