I use this system regularly & over the years have found it to be generally quite reliable. It also gives you plenty of warning(s) if it's not functioning as requested or when you change a parameter. I always teach the importance of thoroughly understanding what you expect to see before selecting any mode / function and thereby you should be immediately aware of a problem. As others have said .... very close monitoring of the system and aircraft attitude is vital. I watch with interest to see what we can learn from what sounds like a close call.