or better than #4 this workaround https://www.caterhamlotus7.club/comment/2400087#comment-2400087
perfectly spotted by aerobod
On an iPhone or iPad all you need to do is make a small edit (such as crop or change the contrast) when the jpeg version of the photo is in the desired orientation and re-save the photo, updates the EXIF tags for compatibility with this site. No need to transfer to another platform or use any other editor not standard on the iOS platform.
having said that my little exploration is about WHY this happens trying to guess the droopal (drupal) code issue.
The other day/week I uploaded a pic using every which way and still it was wrong.
So I cropped it a bit narrower and presto! It was the right way up.
So theory is pics might need to be in portrait not landscape
Or hypothesis 2 there is a width restriction which if exceeded the pic is swivelled.
of course if we could see the code we might be able to see the parameters .