Do you also have image upload issues sometimes? I have posted a screenshot of how it looks when it fails. It is a known bug -> https://github.com/LemmyNet/lemmy-ui/issues/1489
Do you maybe know how to get around it, and still be able to upload the image?
It works with a smaller (450KB) image ~
Maybe interesting or not but I've been using .webp images as an alternative to .png, as they offer the same lossless quality at almost half the size sometimes, or .webp at 99% quality, which will of course give huge savings in file size while keeping all the relevant details unless pixel peeping of course.