Either Heliosphere uploads dupes of images, or it has these placeholders in between each image. I've tried removing them and re-uploading the images, but the problem persists. It was an issue for other mods, but this is the first time it's inserted placeholders between images.
I don't think I do anything odd, but:
I will upload the images as normal, sometimes the images will then bug out. I will go to edit the listing to delete the extra pictures, save, and an error will say no new changes. Then sometimes all the images are deleted. I just keep repeating the process till it just gets it right.
This specific bug in the screenshots is the first time I got that variant, but it went away on it's on after a moment. No edits necessary.