I have found that even if the images look right on my desktop, sometimes it helps to go into an image editor and rotate them in one direction, then back to the original direction and save the file and this “fixes” it.
Thank you, @falcusd. I followed your suggestion and rotated the images prior to importing them and this did fix the issue. As you said, it would be nice if Gallery did the right thing but at least I have a workaround for now!
