summersummer solved the problem reported by installing the Image Rotation Repair, which describes itself as follows:
The Image Rotation Repair plugin simply fixes image orientation based
on EXIF data. This is primarily a patch for mis-oriented images
delivered from iPhones. Functionally it filters all uploads and if
EXIF->Orientation is set to a number greater than 1, then the image is
resaved with a new orientation before the image is processed by
WordPress.