Sorry for strange title - I wondered how to describe it in short and accurate.

Steps to reproduce:
1. Open two windows - for example gnome-terminal and nautilus.
2. Maximize gnome-terminal by double-clicking on title bar.
3. Switch to nautilus by clicking its icon on panel.
4. Hover over one of icons on title bar (minimize to panel, minimize/maximize/quit).

Expected result:
Icon is highlighted, pressing it does its action.

Actual result:
Icon does not react to cursor being hovered over it and clicking on it makes focus is switched to gnome-terminal.

This can be especially nasty in this situation:
1. Open evolution, it probably will be already maximized (if it is not, then use the maximize button)
2. Open gnome-terminal, if it is maximized, then minimize it and maximize it by double-clicking on title bar.
3. Switch to evolution by clicking its icon on panel.
4. Click the 'x' on its title bar.

Expected result:
Evolution is closed.

Actual result:
Gnome-terminal is closed. Nasty!

Double clicking on title bar to minimize it does not have this problems.

Metacity 2.28.0