Looking through another forum a while back, I saw a post stating that this was one of their non-gps aircraft. Therefore, more likely to have a slight error in the calculated vertical path.
To be honest with you, I have found that the calculated path on these VNAV approaches corrected by GPS to be amazingly accurate right down to 50 feet. And who out there has not been in a situation of extremely murky minimums with the pilot just barely able to have the required visual reference and then continuing inside on instruments for at least a few more seconds until the picture is clearer.
But if the path is incorrect, and the references you saw at minimums were actually something else, you could be headed toward something else beside the threshold plus 50 feet.
Is this plausible?