I don't know what is the problem, but I have the same issue. I've been working as a professional photographer, and it was a huge problem, but thankfully I found out how to fix it. Like you, I also asked for help on a forum, and someone, whose name is Nick, recommended a site that I can use for photo editing. The site I was recommended by Nick allows to change the photo's size without losing the quality, but it also allows improving the photo quality. If you want, you can check it and find more options allowed on it.