I made an egg(!)speriment: When I got a hatchable gold egg and a normal white hatchable egg I placed both in the same coop. They would both spoil but then I would grab them and drag them around. Even dragging them to the sims inventory and back to the coop. The Gold egg became "fresh" again, but the normal kept being spoiled. - I think when they disappear from the coop its because sims clean them up, like spoiled food in inventory or fridge. - Maybe a fox if your sims out?
I had to keep doing it until it finally hatched. I now have a little gold chick, but seems impossible to get any new normal chicks to hatch.
Its probably due to a bug the golden egg hatched, because I can sometimes do the same with fish, eggs and other spoilables in a sims inventory. But I hope no-one fix that bug! If I had left the golden egg untouched it would for sure not have hatched...
Im on a Mac so I dont now if a save is needed from me? But if needed I might be able to make one when I try again?
(Or maybe it was fixed in the patch I can see is available today??? Im just not playing on any of my farms right now)