Looks like the only significant difference of those images is that they have additional background color and physical size chunks, I guess pnglite doesn't support the background color:
Background color: white
png:bKGD: chunk was found (see Background color, above)
png:pHYs: x_res=3779, y_res=3779, units=1
Can be checked with magick identify -verbose skin.png
and fixed with magick convert -strip in.png out.png
. Confirmed with client version 15.7 that the converted skin loads. Can we add a check for this in the upload bot and fix existing skin in the DB?