Using Avalonia 11-preview, assigning PointerEntered event, making Opacity=0.8, and PointerExited event, making Opacity=0.0, to a control (e.g. a panel), once the opacity is set to 0.0 in PointerExited, the control doesn't answer to PointerEntered anymore.
AvaOpacityTest11Preview is a cross platform solution using Avalonia 11-preview. Compiling the Desktop project you'll see the bug described above.
AvaOpacityTest01018 is the same project in a solution using the latest stable version of Avalonia (0.10.18). Here the events and the opacity work fine as expected.