bucanero
Developer
yes, in those cases you'll have to manually replace files. With a different title-id the game won't even detect or show the save, with a different keystone it will fail to load with a "corrupt" message or similar.
Keep in mind that Apollo has an option to export and replace keystones, so you could use that solution if you only need to replace a keystone. (in the end the process is similar to replace the data files, but you swap keystones). Also note that replacing keystones should be done before you try to load the save-game, because once the ps4 flags the save as corrupted even if you swap keystones it won't work.
Yes, the old "save mounter" method is done with decrypted save files and you're only replacing the data file content, that's why it should always work as long as the save is for the same game. That's also why you don't need to resign, change keystone or do anything, because you're using your own save as a "container" to inject the data file from another console or user.
As a general note, that's why I have been pushing for PS4 save-games to be shared in decrypted format, because there are too many things that can go wrong, and if you have a decrypted save you can just take the data files and do whatever you want, inject them, import them, resign, etc.
Bottom line: if you're sharing a save, use Apollo and always use "Export save-game to ZIP". (or copy decrypted to USB). With a decrypted save everyone will have less troubles.
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