Steps to reproduce :

1) Launch SwingSet2 with -Dsun.java2d.metal=true
2) Click on "Look & Feel" menu - a menu with 4 menu items pops down
3) Hover on menu items up and down using trackpad (Do not click)

It can be seen that sometimes more than one menu items are shown as highlighted. See attached screenshot of the menu.

Tested on MacBook Pro 16" with discrete graphics card (macOS 10.15.6)