QMenu has two methods to activate items:

1. press RMB (menu shows), release RMB, move to item, click on item -> menu closes and executes item

2. press RMB (menu shows), move to item, release RMB -> menu closes and executes item

The problem: If you wanted to use the first method, but slightly moved your mouse while clicking to open the menu, Qt could interpret the move as for method 2, and execute the item just near the click point, while you expected it to stay open to click on a different item. This is especially noticable with styles that do not have large margins for the menus (e.g. Plastique).

One way to solve this would be to require some delay (e.g. 200 ms) between click and release for method 2 to execute.

For more information, see https://bugs.kde.org/show_bug.cgi?id=168979