So the header for a JPEG should start with FF D8 and end in FF D9
So maybe check if the files at least end correctly, if they do you could try adding the magic bytes back.
I'd secondly try opening the file in as many applications as possible, one might be a bit more lenient/smarter in pulling the image out of a not-quite-right file.
Finally you suggest they're all the same header, is everything else on the drive fine? Is there a chance some cryptolocker malware has had a chance to run over the drive? I'm suggesting as the files could have been encrypted in some way and this is what's preventing you from reading them
Edit: worth noting I used an S2 years ago and had no problems getting the images off back then