Expedition cannot spawn on Mire maps

For some reason Mire dodges expedition whenever I put expedition tablets in a tower. The number of maps that the tower said it was going to affect was much more than the total number of maps in range, so I can only conclude that Mire is flagged as No Expedition or something. I assume this is on purpose for some arcane technological reason, but just in case it was an oversight I thought I'd report it.