Dixie, a beautiful year-old GSD, lost her down/stay. The cue simply stopped working. Rather than being upset, her owner went back to basics. She revisited her "stay" homework from Dixie's original puppy class. In a week, Dixie was staying better than ever. What happened here?
A bit of history: Dixie has been training regularly since she was a young dog. She learned her basic behaviors early on. Once the basics were solid — duration, distance, and distraction were added. As time went on, Dixie learned increasingly more difficult behaviors. For example, Dixie has an awesome "dead dog" (dog lays on her side, head down, no movement) on cue.
My best guess about cause in this case is 1) Dixie and her owner got caught up in learning new and fun behaviors and forgot to practice the basics, or 2) circumstances (for example, a busy time in the owner's life) prevented regular practice of learned behaviors. Whatever the cause, Dixie didn't forget what down/stay meant. She got a little lazy. But because she has a devoted owner, Dixie got her groove back!