I've checked the screenshots and can clearly see that all 4 'submission.pdf' files have different content (if you are using coversheets, then that could be explained by them having the same initial file, but having different data in the coversheet, but given that the original files were different, I think that is unlikely).
As I stated in the last message, you need to look in your 'moodledata' directory on your server - I cannot tell you where that is, it depends on where it was placed when you first set up your moodle install (although looking in the main 'config.php' file in the Moodle code folder for '$CFG->dataroot' will tell you where it is located).
Once you've located the moodledata folder, you then need to find the 'filedir' folder and then look for the files in the subdirectories there. If the 'contenthash' of the file is, for example, 'cfe0640de78cf2a42...' (rest ommitted to avoid me typing any more), then the file will be found, on the server, in:
If you copy that file out (do not alter it or delete it where it is!) and then rename it to end '.pdf' you should be able to open it in Adobe reader and check the file is what you expected. You should find that, for each user, the files in 'submission' should be the same as the file in 'submissionfinal', with (optionally) a coversheet attached and all files combined together (if there were originally more than one file submitted).
The 'submissionfinal' file should also be what you get if you click through to annotate the file in Moodle, or if you click to download the file. If, somewhere along the lines, a file is not matching up with what you expected, then that would be a bug that I need to investigate.