Some recipients may see an image rotated in a different way than it appears in the template you created. Most recipients using Gmail as their email provider will experience this problem, but there could be others.
Metadata (or EXIF Metadata) is information stored in the preferences and properties of an image file. It can include the location of where the image was taken, details about the camera that took the photo, and much more. While it appears correct in the template, some email providers read the metadata from the image instead of how you intended to show the image. So, if the image was originally taken at that angle, it has markers on it for that rotation that the email provider reads before it reads your settings. We don't have a way of preventing Gmail (or other email providers) from reading the metadata, but we can make sure the image doesn't have those properties before we send it. You can remove the metadata from the image before uploading to the template.
Here are some outside resources for how to remove metadata from an image.