I use Paper 1.16.1 for challenges with 4 of my friends, everything goes smoothly until The End.
The dragon will just spam fireballs way more than in single player, especially if there’s only 1 person in the end. When the dragon perches he only stays there for 1 or 2 axe hits, which is also not the same as single player. And also the dragon will disappear client side when it flies too far away (im assuming this is a render issue?)
The first 2 are the main issues, anyway, any help is appreciated