When playing Oak and you have summoned a lot of your flying spirits and you have everything selected they form a long line.
If you get too close to the edge of the map you can loose spirits if you unselect them all because you can not see them, meaning you must scroll out to find them.
If this is not a bug then it should be implemented so that they can't fly off the map if you get too close to it.
Thanks,
YouR-LasT-NighT