Hello @MortenCopenhagen,
this is exactly what I reported a couple of days ago but using the desktop browser.
Originally, I noticed 3 photos missing, but after uploading more, I saw the same behavior, you observed now.
Using the browser, the first batch contains the 10 newest photos. If the eleventh or more photos belong to the same listing as the tenth, the eleventh or more are missing. I confirmed this behavior several times and no photo is missing, if the tenth and eleventh belong to different listings.