alt key + right mouse returns middle mouse click

when detecting rselect on any panel with alt key down, the panel object returns a middle key press on td 0999 all current versions.

Yeah, this is a new option in preferences, introduced as a default because so many people are working on laptops these days without 3 button mice.

You can turn it off in Preferences > General > “Use Alt_Right-Cliuck alternative for Middle-Click”