Both ways back are authentic v83 content on this map: Simon the Temple Guide and the walk-out portal both exist in the original game data for Shalom Temple. We keep it faithful to v83, so this one is working as intended rather than a bug.

Reopened and fixed. You were right, and my earlier reply was wrong. I re-checked the original v83 map data for Shalom Temple: it has no portal back to Happyville at all. The only way home is Simon, the Temple Guide, exactly as you said.

The extra portal came from one of our own tools, which adds an exit to maps that look like dead ends. It only looked at portals, so it never noticed Simon and gave the temple a second way out that the original game never had. I removed that portal and fixed the tool, so it now counts NPCs like Simon as a way out and won't put the portal back.

This is LIVE on play.mapleverse.online now. To re-test, ride Simon from Happyville to Shalom Temple. There should be no portal on the map, and talking to Simon should still take you back to Happyville.