All player's spawn is set to the same location when pressing spawnpoint button.

Interesting it should not do that. What other mods are you using?

The mods is based on "event.player_index" so I don't see why it would effect all players.

Any other details would be great.

Spawn points are tied to forces, and not individual players. In a typical multiplayer game, all players are on the same players force. In PVP servers with multiple "teams", this would mean that all players on a given force would share a spawn point as well.

The method for setting spawn points belongs to the LuaForce class, specifically set_spawn_position, which you have used in your set_spawn function.

As far as I know, there is no way in the API as it stands to set the spawn point for an individual player. The only workaround to achieve this that I can think of would be to implicitly create a force for each player when attempting to set "their" spawn point.

Wow, I never responded to this after the fix. All locations are stored in a new variable stored in the map. On re-spawn it checks who died and teleport to the correct location.