When positioning a *Flash Zone* over a terrain element (Nexus, turrets, walls, etc...), it will be positioned on the closest position where the center can be on *walkable* terrain. (My guess being that the unit giving the buff is not allowed to go there).
* This behavior is not intuitive (no way to guess that it will do that)
* Placing a *Flash Zone* on terrain allows to flash back and forth if necessary, which is currently really difficult.
Easy to reproduce, just place a *Flash Zone* on a piece of terrain (cf. screenshots)
My cursor when casting:
Result on the Nexus:
Centered on an inhibitor:
Centered on a turret:
Cursor over large terrain (Sorry for the upper part):
Result over large terrain (Sorry for the upper part):