Rejected scan of stereocard - any advice please

Hello – just had this one rejected for technical reasons.

I was wondering if anyone could help identify the problem and let me know if it’s the sort of thing that I could fix in post.

They are two scans of a tinted stereo-card from around 1870. The top is an ordinary scan the 2nd is a transparency scan.

The original image is printed on translucent paper and painted on the back so the colours are only visible when the card is back-lit. To bring this out I scanned it as a ‘positive colour transparency’. I don’t know if that’s the right method for this sort of image, it’s my first attempt using the transparency setting.  Any advice would be appreciated – even if it’s only ‘give up, cause it’s not gonna work’.