Bug Big Reactors Problem

[Bowlcutinmatrix]

I have no idea what happened to this reactor. My friend decided to expand his and now its registering a block that isnt even a part of the generator as "not usable". Every time I expand it in the X axis, the not usable block also moves accordingly. Any help?
I also have a video of the problem if anyone needs it.

Thanks in advance

 

[immibis]

What block is at those coordinates? Keep in mind that since your position is -982.7, when you round it down it's not -982, it's -983. So -982 is the block next to the one where you are standing in the screenshot.