I think that when you have two starports (or other unit making builds) and you train units in both at the same time one seems to finish quicker than the other. Also its annoying when I'm sending S-trikes to my defense bunker and there are will near the bunker the S-trikes sometimes get block by the wall and force me to move a wall in order for them to get in the bunker.
 "Galaxy Life"){kind=icon}
 "Stick War"){kind=icon}