Two Dragon Eggs

I have two dragon eggs in my Minecraft survival no cheats world. I have beat the Ender Dragon 17 times in that world, but the first and second time, it spawned a dragon egg.

Steps to Reproduce:

1. Create a new world
2. Go to the End
3. Kill the Ender Dragon
4. Reload the world
5. Re-summon the Ender Dragon by placing four end crystals on the edges of the exit portal, one on each side
6. Kill the Ender Dragon

Observed Results:
A second dragon egg generates on top of the first dragon egg.

Expected Results:
The dragon egg should only generate when the first Ender Dragon is killed.