Mobs spawn outside region

I have made a dungeon with several layers and rooms. The whole dungeon has one region with high priority. This region just has the no pvp flag. Right now I have two other regions. One region on the top of the dungeon and one inside. The problem is that the both mythicmobs spawn in both regions, even though I have set a -inregion "region" condition for them. They are supposed to spawn in diffrent regions.
The regions does not overlap, or even touch. There is several blocks between them.
Why...

Mobs spawn outside region