…the simple fix, if you have access to edit the ad, is to download the sideways picture, then open it in Windows Paint and do nothing other than save it. Then upload the saved picture back to your ad and it’s rotation should be fine.
If all that sounds like Greek, or doesn’t work for you, just send me an email and I’ll fix it for you: email@example.com
Otherwise do nothing. I try to come along a few times a day & fix them anyway.
Pretty sure the rotation problem will be fixed in a future classifieds update. It seems to only affect some, but not all mobile uploads.