Putting the controller in the "right" side of the foundry structure makes it invalid

[radwadas]

I'm playing FTB Stoneblock 4 and found a strange issue with the foundry. As seen below the left one is dark and it's considered invalid structure (Invalid or missing structure block at...), the right one is working.

Moving the controller block to the left corner or even rotating it will make the structure valid.

[bookerthegeek]

If I recall correctly, the corners are not supposed to be valid? I am surprised it works at all in the corner. I think the error might be it works at all in the corner.