Update (7 months): No other problems outside of initial days.

Day 3 and it wiped out all tabs (except one). Tabs on bookmark-backup gone, folders do remain. From restore backup, yesterdays backup didn't work (it showed that it would have the tabs, but nothing. 2 days ago backup did work.

Only automatic backup option is one-file-a-day (erases previous same day backup)

Update: seems like "yesterday"-backup worked after some other backup worked.