I am a plugin developer, and the plugin I work on most is a multi-world management plugin hat utilizes the WorldCreator class to generate worlds. I noticed, while I was working on an update for 1.16, that the exit gate in End words created by the WorldCreator class were not working correctly. When a player uses the exit gate in an End generated by the WorldCreator, the PlayerPortalEvent is called instead of the PlayerRespawnEvent. This causes players to end up in the default world's end instead of the overworld.

To be sure it wasn't my plugin, I created a dummy plugin that simply instanced the WorldCreator class and generated an End world. After quickly killing the ender dragon, I hopped into the portal and found myself in the default End like before.

To recreate this,

1. Generate a world with the WorldCreator class
2. Teleport to that end
3. Kill the ender dragon
4. Use the exit gate

I tested this on 1.15 and 1.14, and the exit gates worked fine on those versions. I tested with spigot builds on 1.16, 1.16.1, and 1.16.2 and the exit gates were not working on any of those versions.