It does seem to be a mixture of website and user error. I make sure my images are all orientated correctly in my camera roll but the odd one would occasionally flip itself around when uploaded.
All the pics in my camera roll are the right way up. They were all the right way up when I added them to my ad. When the ad was posted, it flipped the first pic.
This happens to me all the time. Photos are fine on my phone but flipped on the advert. The simple fix is to do a headstand when viewing the classified ad...
Happened to me for the first time recently, not an ad, was posting a meme, had to keep going back in to my files to rotate the image, tried every angle but it kept coming out wonky, after 6 or 7 attempts it seemed to sort itself, which kinda makes me think its an occasional glitch at the hosting company ?.
For ads i don't think its a big deal though.