I don’t either. The two diagonal lines in the OP's highlighted area appear to be part of the image: a water stain on the wall beneath the circular window, and some geometry (possibly a corner of the building or a column) that is closer to the camera than the window and partially obstructing our view of the window. I don't see any problems with the negative but maybe I'm just missing something that others are seeing. Here's the highlighted area inverted:
It can certainly looks like just a shadow but it's not. The problem area has the look of a double exposure if you can imagine that. The density does not look 'natural' or in keeping with the surrounding areas, if that makes sense.