ValueError: operands could not be broadcast together with shapes (7256,7302) (7256,7301)

[lizard1111]

I got this error when attempting to apply a flat to a folder of images.

At first, I assumed my flat generator had produced an image with slightly wrong dimensions, so I brought my flat.tiff into photoshop and increased its size from 7301 x 7256 to 7302 x 7256.

Using this modified tiff fixed the issue.

But then I realized, the flat.tiff was not too small in the first place. Its original size of 7301 x 7256 was correct, i.e, the same dimensions as my folder of tiffs to be destriped.

After processing, the destriped folder also contains images of 7301 x 7256.

So my question is simply, where does the 7302 come from?