The dragon egg never appear

Descripción

I and my friends went to the end to defeat the ender dragon on a Realm, and when we finally kill the dragon the egg never appeared. I test then I tested several times in a creative world and sometimes the dragon never summon the egg, or I kill it invoke once or twice and then the egg never appear again.
(Minecraft 1.16.100)

What I expected to happen was...:

I expected to be able to kill four times the dragon with my friends.

What actually happened was...:

The egg never appeared and we kill it just once.

Steps to Reproduce:
1. Kill the ender dragon
2. If the egg appears, invoke the dragon again and kill it.