unshred layer

[Krikor]

@retroarchgirl, this error that appears is possibly related to the relationship between the dimensions of the image and the Strip Width you want to use.
The values 535 x 249 are not multiples of 32.

I suggest you:
1- Increase the canvas size of this image to something like 544 x 256 ( Image - Canva Size;
2- After applying the plugin vertically and horizontally do: Image - Crop to content.
    (it is possible at the end to use the crop tool to adjust the excess edges)

I also suggest that you read again the suggestion given by Ofnuts in post #3. You will discover a different way to proceed in this type of editing.

Note: At least in the copy of your image that I downloaded, the tiles are not 32x32, so I think the cropping will not be correct if you use the value of 32 for the Strip Width. (It was more like 18x18px)