Failed to convert JPEG-XR image

Hi,

I am converting two .kfx files to EPUB. First file converted without a hitch, second file reported the following error message in full:

Exception during conversion of JPEG-XR 'resource/-y3Wvp1LTU_AckVIlnqBQA2237.jxr' to TIFF: NotImage: Failed to convert JPEG-XR image

These two books are part 2 and 3 of a series, so I completely failed to understand why 1 converts and the other does not.

Any help is very welcome!