It was my only disappointment with SFOS. It’s their code, their backup system, they should have foreseen that people were going to upgrade to new devices using previous backups.
At a minimum the system should gracefully fail with a message “it seems you are trying to upgrade from an incompatible version” rather than what it did, which is hanging in the middle of the process, leaving the user confused and making a bad name of SFOS. By “bad name”, I mean a year later people write the backups are unreliable. Which is not the case, the backups work superb, the binary format is preserved even when skipping versions, yet it fails on something apparently simple to detect, and not all users will figure out the right keywords to find a solution on the net.
When it happened to me I did not think first thing to look on the forum because I expected the binary import to fail for one or more of several reasons: different phone model, skipping system versions, moving from the free to the paid version. I accepted my fate, then took some hours to solve it by myself (understanding which files were there, figuring out how to dump the messages and calls from the database on the old phone and how to import them on the new one) – I told myself I’m lucky the old phone still works, otherwise I would have only useless backups, and my message history would be lost.
About when I was finished I finally understood the issue was only a change in the user name and my backup had been safe the entire time. It did not make me very happy, though it gave me opportunity to learn a few things about the SFOS data structure.