Hi
I found the answer to my own issue ;)
Here it is to the benefit of the group.
Each of my OCX file have this syntax in Inno: Source: "ctcalendar.ocx"; DestDir: "{sys}"; Flags: restartreplace sharedfile regserver
The solution: The flag "restartreplace" will register correctly the component when and only when the PC is rebooted.
Most of the components above DO register at once when running INNO.
However, if the component is busy or otherwise "not available for update", it will be register after a rebooth is performed on the PC.
It looks like there is an entry saved automatically somewhere to signal to Windows to register any pending - not yet registered - component when rebooting.
Voilà!