Here’s an odd symptom – vertical photos from iPhone or iPad end up horizontal once uploaded to WordPress.
This was originally a vertical photo. After uploading to a WordPress post, it shows up horizontally.
This was and is a horizontally oriented photo. It presents as such in WordPress, no editing necessary.
This is also a vertically oriented photo. It appears normally here after editing. I opened it in Preview (my default jpg app) by double-clicking. I rotated left, then rotated right, then saved it. The double-rotation just leaves it exactly as it was, visually. Then I uploaded it to WordPress.