Jeez it's been 11 months and still haven't been resolved? I'm facing this exact same issue and I'm reading in other threads that it's an ios issue and still not corrected is this true or are we still missing something?
So I made a little script to test this. If you take the actual photo of your iPhone and upload the image, you get a popup with the Orientation value. It tells me it's 6 (which means the photo is sideways but corrected through the iphone as right side up).
This is where it gets confusing. So before uploading, the user on the iphone has an option to resize to large, medium, small (anything other than actual size). This is where the problem lies.
Because if you choose any of these, then the image uploading now says orientation value 1 (which means it's right side up) however the image thumbnail is sideways!
So after digging through more, there was a vague mention that iOS 'copies' a brand new jpeg just before the image is uploaded. This means that this new smaller resized image is a version of the original actual size, however the orientation exif value isn't carried over. It's defaulted to value 1!
I wish there was a way to fix this on our end, otherwise the exif interpreter doesn't know if the image was already right side up and given a default value as opposed to the ios making a brand new resized image and carrying over that sideways 6 value.
Does that make any sense ? I hope I didn't confuse anyone.