We aren't deities.
You need to show us the code (from <head> to just past the first text that shows), the CSS sections for all classes referred in the code, AND the image size info.
Then we can make an informed comment.
BTW If it ONLY misbehaves on a single device family, the problem is probably a quirk. There may be a work-around. Calibre and Sigil use the same render engines, so the count is only 1 test.
(Quirky) ADE is a good test as many devices use that.