this is a known bug of trigger redeployment when creating a mission.pbo from your user mission.
It is thought to be caused when there are too many objects on the map
(eg when you have lots of additional buildings, sandbags etc)
It more commonly occurs when using rectange triggers set at an angle which is not 0, 90, 180, 270 degrees
Try using an ellipse trigger and set its angle to one of the above