SpawnActor isn't calling blueprint constructor UE4

Strange issue that I’ve encountered today. I have a C++ class ATileFunctionRepresentation that extends AActor. Then I have a Blueprint that is parented to ATileFunctionRepresentation.

Instances of the blueprint are spawned in the editor when the level-designer changes a boolean property of AUGTile objects. This is achieved via:

FunctionRepresentation = GetWorld()->SpawnActor<ATileFunctionRepresentation>(TileGrid->TileDetailPiece, GetActorLocation(), GetActorRotation();

and I can see from the World Outliner the blueprints are indeed spawning. But the problem is that their constructors are not running. Only when I drag them using the transform widget do the constructors run - and I’ve no idea why. It’s as if they are spawning with bDeferConstruction set to true, but in that simple line of code above, that shouldn’t be the case.

Any ideas?