Are your friends using Windows? If it’s actually a JPG file, I’m not sure what separate issue you could have with it – which is why I wondered if it is mislabeled. You can use an app like MediaInfo to see if it’s a different file type in disguise (it works for images too).
The big picture work-around for this is to have one of your friends copy the images for this deck into a zip file, and share it with you so you can download it. Then you can unzip it to make sure you can read the files, and then copy them into your collection.media to overwrite these broken ones. That won’t tell us why you’re having this issue, but it will get you up and running again.