@marqm Appenend to me 3 or 4 times in the last days...
the only thing i can add is that when i click on my user icon (top right little person) it says tha Opera Sync is OFF, but when i click it in settings it says that is ON...
Seems something related to crash occurring when moving tabs and some sort of weird behaviour of the Sync feature.
Hope this will stop occurring.
I've saved all my opened tabs (for all workspaces) in pinboards to restore all of them when necessary.