回复：see if this picture helps (图)

In the beginning I was suspecting the wall was bulged.

But it's not bulged in one direction. It's very minor bulges in multiple direction in one set of wall.地下室墙面都有些凸噢不平. Plus all the walls in the basement looks like the same. It made me agree with the first guy that it was the way it was built.

I wish I took pictures.