I too have had this problem on numerous occasions over the past couple of years. For me, when this bug occurs it actually erases everything and goes back to the previous song. After experimentation, I have found that I can recover by going to File, Undelete bars. While it is a real PITA when it happens, at least I don't have to start over now that I have found this.
I reported this same thing a year or two ago, but nothing ever became of it. I also am unable to "Make" it happen, but for me it is usually centered around copying/pasting.