Although you may have had mob spawning game rule off, a mob that had spawned before the game rule had been changed May have activated it. If you are sure that that's not the case wait and see if that happens again if so,Maybe re-wiring all the red stone around it would help. And if it doesn't happen again continue to build the rest of the map and if it activates itself again then be cautious, try to figure out the timing when it goes off so you could use repeater locks to stop it from triggering. After this if it continues to happen I would try to move the command block which contains the tell raw and/or the way of triggering the command block e.g from pressure plates to /test for command and vice versa. If all else fails, remove the command block unless it is essential or try to rewrite it into a book. If it continues from then on I honestly am out of ideas.
