Unfortunately yes I have had that experience.
Including having to break the rigamortis to get them out the door. But they were on the freight manifest not pax.
Completely the wrong aircraft for the job, double bagged strapped down in the gangway. But we got them home within 24hours so the family was happy how ever we managed it.
And if they died in a chair going through security you would have 3 hours for them to go stiff and they are stiff warmish for about 5 hours. And old codgers aren't the warmest to touch anyway. And lets face it I have lifted old folk onto the plane in my arms some the emergency door feels heavier than.
Yes yes I know we shouldn't but when the wind is to high for the ambilift and you have been flying the old dear to her hospital appointments for leukaemia for the last 6 months and her stomach feeder is leaking and she needs an op and you get a big kiss and a smile for making it work needs must.
Never had one go mid flight though. I still have the paperwork from the repatriations though. Was never told what to do with it at the other end once they had been signed over.