In my experience, iPhones are the worst offenders here, but Androids are not immune. The phone was not stabilized in either the portrait or landscape mode before photo is taken. The photo is actually taken right side up, but the phone still thinks it’s in another position. When you view the photo on the phone, the hardware resolves the issue for that viewing and it “usually“ shows you your photo in the proper orientation. Unfortunately, the Exif data embedded in the photo shows the wrong position. Our forum software takes the Exif data and orients the photo the only way it can.
The worst photos are those where the phone is not perpendicular to the ground. Shooting up or down, the phone’s gyro may not catch up in time to update the Exif.
Pro-Tip (I am a photographer) - kill off all your apps on your phone before start snapping photos. Then, hold the phone still a moment before snapping your photo. If your phone’s gyro is working properly, the Exif data should be good and correct.
If you load your photos first to a PC or Mac, you can generally adjust the orientation of the photos.
I do not believe that this forum software has the ability to reorient photos…. If it does, I sure don’t know about it…