Invisible "untitled" window in Safari.
After browsing for a while Safari always lists an "untitled" window that doesn't exist. You can see it in the Window menu of the menubar, and in the dock when alt-clicking Safari. But there is no window.
There is a moment when it seems to appear, when you can see that something is opening, because there is a brief flash of the app, as if a pop-up is opening but nothing appears. After this the app lists an untitled window that can't be found.
As previously reported elsewhere, here for example, sometimes Safari creates an "untitled" window but when you select it there is no window, nothing shows up.
Using expose doesn't reveal an additional window. Disabling and removing extensions and resetting Safari doesn't change this behaviour.
Latest version of Safari (15.x), latest version of macOS (12.x). Have run full drive scans with Bitdefender for malware and nothing turns up.
What could this be? What other steps aside from the basics (resetting safari, clearing data and caches, safe mode, etc.) can be used to identify what this is? It doesn't show up anywhere in Activity Monitor either.
It feels like there is something running that shouldn't be running and it's using Safari but I can't identify it. It seems to only occur on my M1 mac but not on my Intel mac.
Mac mini, macOS 12.4