When moving the mouse cursor to the very top edge of the screen, the macOS/Opera top menu bar area triggers. After moving the cursor back down, the browser tab bar becomes completely unresponsive to mouse clicks. I am unable to select or switch tabs for roughly 5 seconds until the menu bar's invisible hit-box overlay fully clears/closes in the background. The cursor moves normally, but clicks simply do not register on the tabs during this timeout. Ctrl + Tab still works perfectly fine during this 5 second freeze, confirming it is an invisible UI overlay issue blocking mouse input.
[I can't upload a screen record of the issue so you'll have to visualize it with this screenshot]