I had the same problem with my zombie spawner in survival and made a copy of the world to try and fix it in creative mode and if you put an egg in it ( I tried skeletons) it spawns one set of the desired egg and then continues spawning zombies despite a skeleton spinning inside of the spawner. Then i tried putting a zombie egg in it and everything inside the spawner disappeared, but the zombies still kept on spawning. After that the spawner didn't react to any kind of egg.
Clemens Gehrer
I had the same problem with my zombie spawner in survival and made a copy of the world to try and fix it in creative mode and if you put an egg in it ( I tried skeletons) it spawns one set of the desired egg and then continues spawning zombies despite a skeleton spinning inside of the spawner. Then i tried putting a zombie egg in it and everything inside the spawner disappeared, but the zombies still kept on spawning. After that the spawner didn't react to any kind of egg.