Problems With Sailfish Backup/Restore Function?

Seeing that quite a few people were having problems with the UI update from 4.3 to 4.4 I decided not to risk updating my main daily driver XA2 phone in case it got screwed up, or a key app that I need wouldn’t work with the new Sandboxing functionality.

Instead I decided to do a new flash of 4.4 to my spare XA2 which I had been keeping with Android 9 on it as a comparator to my Sailfish XA2. If it worked then I would transfer all my stuff across and this would become my new Daily driver and I would then UI upgrade the old 4.3 daily driver to 4.4 and keep this as a spare.

Flashing the new phone went fine, and all my apps seem to work with Sandboxing so far - so all good.

To get some of my stuff across from old to new XA2 I took a backup on old 4.3 XA2 and restored it to new 4.4 XA2. The rest I SSH’d into both phones and simply bulk copied files (music, pictures, etc).

The backup seemingly brought all my accounts across (mail, caldav, carddav, dropbox, twitter, etc), but obviously with no passwords. On every account, when asked to sign in again, the correctly entered passwords were rejected. I had to delete all the accounts and re-create them from scratch.

Neither did the backup bring any emails across, or contacts, or calendar entries - but since these are synchronised with Office 365 and Synology servers this didn’t matter too much (I did wonder whether the backup of these items only works for locally stored email, contacts and calendar ?).

Finally the backup didn’t bring any other settings, app configurations (the apps on old and new phones were identical), documents, ambiences, or anything else across.

The backup did bring my text messages across, and my notes from the Jolla notes application, but that was it.

So I am wondering, did I try to do something with the settings/backup functionality that wouldn’t work (e.g. because it works differently on 4.4 from 4.3 - even though the two XA2 phones are identical models), or does the backup function actually not work at all, or is what it actually backs up so limited that its really of no use at all in keeping key phone data, accounts, configurations secure in the event of a failure?

I only ask, because whilst I knew the backup function didn’t secure ‘bulk data’ like pictures and music, I did at least think it covered the basics. But now I’m not so sure I want to trust it to do even the basics … ?