This (double tab creation) just started happening probably between one and two weeks ago. I did install the current version update at around that same time, so this tab duplication issue may be related.
For me - Opera has been a bit spotty with auto-updating. Sometimes Opera will say it's auto-updating, but after it restarts, it's still the same old version. Often I have to download the latest Opera installation file, shut Opera down, and install the latest version manually in order to update it successfully. But that's a matter for its own support request if it ever becomes bothersome enough.
In 2017 I started using Opera while my primary browser was Firefox. Opera's been my primary browser since about 2019.
Can't live without workspaces! 😊
Have little/no use for Tab Islands... 🤨