What do you mean by "lots of windows with this title/address"? Is there a particular title/address that causes the issue, or do you mean that if there are lots of windows that all have the same title/address?

It's hard for me to test with ~600 tabs, so in general, I wouldn't recommend this extension for use cases like that. But I'd be happy to look into this issue if you can give me a bit more info.

Thanks for letting me know!