MC-93185 was fixed in this snapshot but any worlds affected by it remain broken without an exit portal.

Analysis & Suggested Fix

• ExitPortalLocation doesn't get datafixed to the correct value if the world was generated before snapshot 25w02a. Changing the Y value from -1 to 1 manually via external tools lets you regenerate the portal by following the reproduction steps below.
  
  However it would be best if the portal was automatically regenerated if it's detected that it's Y value is below the world bottom.

Also due to custom worlds the fix it wouldn't be as simple as if(y<1) y = 1. Instead it should be if(y<min_y+1) y = min_y+1

Reproduction Steps

• Generate a world with seed 78539955276621 in 1.21.4
• Kill the ender dragon
• Load the world in 25w02a
• Run these commands
  • /setblock 3 1 0 minecraft:obsidian
  • /setblock -3 1 0 minecraft:obsidian
  • /setblock 0 1 -3 minecraft:obsidian
  • /setblock 0 1 3 minecraft:obsidian
• Place end crystals on the obsidian blocks

Observed Results

• Nothing happens
  

Expected Results

• The end portal would be regenerated
  Minecraft 2025.01.09 - 18.20.00.01.mp4