It's been a long time since I've flown the A306, are you implying that perhaps the missed approach altitude instead of MDA was set prior to the FAF so there was no path guidance and a late descent was initiated when the error was realized?
No. On the A306 once you start down on a profile approach, inside the FAF, you set the missed approach altitude, not MDA. (I don't remember if it's the same on a V/S approach but guessing it is) But that makes it possible to go below MDA without having the field in sight, the airplane won't automatically level off.