I think it's a jpeg issue....Joe?
Not my forte.
It has something to do with settings on your phone and how iPhones format images. Been an issue for years.
I have a Droid Moto Z. I've noticed when I post from my phones gallery of pix that I had taken, the pix come out good as you can see from my previous post in catch photos.
Now when I save a pix from a text that was sent to my phone from my bud, maybe from an iPhone, the pix don't display when the post is opened from the selection of post.