The Melee - Set starting units trigger action puts the bases and units there, get rid of that. The Melee - Force melee victory/defeat trigger action will stop your game from ending when there is only 1 player left on the map.
Your problem is like crazyfool hinted, you MUST place 1 starting location for every player you have in the game. Check the scenario menu -> player properties to see what players you have set, and make sure starting locations are present for all of them. By default, where you put the start location for a player is where the game camera points to for that player at the start of a game. So put them somewhere where you want the game camera pointing at.