@sporty78 That option is for the user to set up how s/he would like the window to open. It doesnt change based on the current window state. And that option will not always work.
Site has all permissions and active cookies (besides pop-up windows and ads).
Looks to be periodic, but recently happens ca. once daily. Restart of browser not affecting this behavior.
Google settings has device and browser saved as approved.
Content in older versions of Opera is the same as Site Settings in the current version. Don't recognize Websites, but perhaps it was in an even older version?