If you would please provide me with some more information, or take a video and upload to YouTube with a link. Information needed.
When you descend how far are you from the TOD?
What mode did you engage to descend and what mode was active when you engaged that mode?
precisely what was the FMA readings before you began descent and what was the FMA reading when you initiated the descent. Were you always below the predicted path or did you catch it and what was the FMA when you did?
all details important video perfect.