Checkable QMenu item indicator stylesheet broken

When we try to set an image for QMenu::indicator:exclusive:checked via stylesheets (assuming we have a QActionGroup that handles the checkable QActions), this generates a non-reversible collateral behaviour: All unchecked QMenu item indicators are sunk.

And setting QMenu::indicator:exclusive:unchecked will change nothing for the sunken border. I tried to remove border, to change the border style, to set an empty image or a non-empty image, ... I also tried to deal with QMenu::item or QMenu::icon with and without :checked/:unchecked, ... Nothing works.

The bug does not appear if we keep the default indicator but if with set an image for the checked state, all unchecked items are sunk no matter what we do (even if we define the unchecked state too).

You can find more details (context, screenshots, ...) about the bug here.

I have tried with Qt 5.12 and Windows 10. I cannot tell if the bug appears with other versions of Qt or other operating systems.

EDIT: The bug also appears with non-exclusive checkable actions (and with or without QActionGroup).