I'm playing with no mods and all game extentions.
Since Seasons pack, had a major problem with sims mass freezing and burning to death (had to remove the option in game settings. They even managed to die inside the house... like the game did not register the space as indoors (it was a basement with indoor stairs on ground floor).
So now i have a family of 2 ghosts and a collection of urns from neighbours who died on the lot in the basement :/ The only thing alive is the cat.
So after a lot of work getting the things together to make 2 ambrosias they simply don't work.
I did try the eat standing up solution, with the same result:
The sim eats the ambrosia and does the resurrect animation (so no waving, but the propper one), but never gets it regular body back and keeps being a ghost.