Folks,

I also find this, it is a bug. Vnav naturally want to try reach the profile but as you say it will often blast past. The way I have found to prevent this is to use the green banana indicator to then descend in V/S mode adjusting the descent as needed. I have found that in Vnav path when in the steep descent, once the descent profile is reached the descent will pass through and lower!
So, for example, if descending to say FL070 and passing FL100 the a/c is in a high descent, engage V/S initially at say 500 fpm to slow the descent rate. One speed is back under control, descend in V/S adjusting the rate using the green banana. I find this essential and effective if flying on line and getting close to the airfield.

Best,

Keith