The bug

The end does not generate and you cannot move when you set the setting allow-nether in the server.properties file to false and then enter an end portal. This can in theory be reproduced in Survival mode (see MC-89399), but as of right now there is no seed with an already activated end portal public. Besides that it can be produced in Creative as well by placing the missing eye of ender items.

The debug screen shows the message "Waiting for chunk...".

How to reproduce

1. Download the latest release minecraft server from https://minecraft.net/en-us/download/server or the snapshot one from the latest snapshot news post
2. Open the server.properties file with a text editor and set allow-nether to false

   allow-nether=false
   

3. Start the server
4. Find a stronghold or spawn a portal to the end and enter it

   /setblock ~ ~ ~ end_portal
   

   → You should be unable to move and nothing should be loading

Code analysis

Based on 1.11.2 decompiled using MCP 9.35 rc1

The method net.minecraft.server.MinecraftServer.updateTimeLightAndEntities() only updates the nether and end if the nether is enabled, however end portals do not check for that. It might be good if a new allow-end option was added to not cause confusion in the future.