The bug from my point of view:
Flea is an all terrain unit that can climb any terrain.
Singulo is on the above pictured hill.
Flea cannot reliably path to the singulo and attack it.
Flea can barely see the singulo without manual micro positioning.
Clicking on the free areas around singulo does not help.
Finding this out in the middle of a game is frustrating, I have units that should be able to attack an elevated building as they can climb any surface. Yet they can't do that due to pathfinding/aiming bugs.
The picture doesn't do it justice, I had a hard time even seeing the singulo without it showing as an untargetable ghost building, despite being right next to it with an all terrain scout.
Yes, it's not cheating. I am mad. Bonus for the pictured knight being unable to fire either, or the reaver. Even though reaver can fire at sky high air units. I don't actually see the singulo on the picture at all from in game perspective.
I don't think it's healthy for the game to have such safe ways of building eco.