Several times I have replaced a linked photo in a frame with the same photo (by name) from LR that has been retouched. As soon as I export the photo from LR, the link updates the photo in APUB. Occasionally, but not always, the replaced photo stretches side-to-side so that people look "fat," for example (the aspect ratio widens). The only way I have found to fix this is to remove the frame and redo the frame and photo. It is my practice to set up a photo without cropping it, so I adjust the frame/photo so that the entire photo is visible edge-to-edge. I have not found out what situation might be causing this issue.