No, they vanished there as well.
I really don't understand it! The only thing I did was logging into Opera sync. And I don't get why one subfolder was for some reason spared from the data loss. There must be a bug of some sort in the sync engine. Because I'm sure I made no mistake...
An update on this.
Seems like there is some sort of time limit of how long they will stick (one week?). I now have only a single instance left. But it is still named (3). I guess it doesn't matter.
Same issue,the synchronization doesn't work anymore.
I have installed a new computer with Windows 10 and Opera, impossible to sign in. It looks like the master password is not used anymore if you have set up previously.
I really like Opera, but the Sync feature is the weakest part of this browser.