@blythe
It happen to me when I change sider bar shortcut to with exit shortcut command + q.
I delete my settings folder of opera and reinstall it. it fixs.
I delete this folder
com.operasoftware.Opera

I use macos version 10 that's why it is under library/Application Support/com.operasoftware.Opera

@blythe "ctrl+shift+x" I think, there isn't shortcut like this. but your case, must be true. I think, at least they must add "reset settings default" to "easy setup" (settings located right above browser)

@blythe
It happen to me when I change sider bar shortcut to with exit shortcut command + q.
I delete my settings folder of opera and reinstall it. it fixs.
I delete this folder
com.operasoftware.Opera

I use macos version 10 that's why it is under library/Application Support/com.operasoftware.Opera