We already have this check in XMenuBarPeer.handleEvent to block all events except paint events:

454 // explicitly block all events except PaintEvent.PAINT for menus,
455 // that are in the modal blocked window
456 if ((framePeer != null) &&
457 (event.getID() != PaintEvent.PAINT))
458 {
459 if (framePeer.isModalBlocked()) {
460 return;
461 }
462 }

It would be useful to have similar check in XMenuBarPeer.handleF10KeyPress. Theoretically, F10 key events shouldn't come to the "blocked" menu due to the fix for the CR 6533175 that redirects F10 key events to the correct window.