This is identical to the issue in
I’m just wondering how progress is going now four years on 
I’d love to look into what may be happening and try to reopen any investigation related to this issue.
Just to confirm, when you preview your project it opens a new browser window every time you press the preview button. And you would prefer a new preview open in a new tab of the same browser window, is that right?
To help us reproduce the issue you’re referring to, can you clarify what setting you have turned on/off? And what browser/OS you’re seeing this with?