DxD asks users to perform Forward Annotation only when:
(1) User closes xDX Designer
(2) If there are pending Forward Annotation, it opens the dialog which explicitly asks users if they want to run FA.
(3) If user clicks Yes in the dialog, then it checks-in the design with Forward Annotation information, and during which operation, the application stays in the read-only mode.
So are you seeing this dialog?
The only other instance where the schematic is always in the read-only mode is when user opens xDX Designer with View -> xDX Designer.
The design becomes read-only also when user selects “Forward Annotation” or “Check In” menu within xDX Designer but it becomes editable as soon as the operation finishes. I have never seen the instance where xDX Designer hangs during this operation, but if that happens, that may also result in read-only mode. So are you running this menu?