What OS? What version of Firefox?

I have this problem too after yesterday's update on my laptop. "Open in new tab" creates an empty window after a pause. "Open in new window" seems to not work properly either. I use these features in nearly _every_ online session!

Windows 11 - Firefox desktop 137

Edit: This is very strange. The Open Link in new tab and new window functions are now working properly. Perhaps fixed by restarting Firefox?

Additional edit: When the menu functions were mis-behaving, a very tall menu would be produced with a right-click on a link. Now the right-click produces the familiar concise menu.

I had the same problem. I use the "vertical tabs" option. I turned off vertical tabs and they all appeared at the top. Then I turned vertical tabs back on and they reappeared.