Tabs in Tab (delete Main tab)

I am encountering a problem using Tabs.

I have a Tab (TAB2) that contains other objects. One of these objects is a uitabgroup (tabgp2).

If I save TAB2 (savetab=TAB2) and then delete it (TAB2.PARENT=[]), If I put back the TAB2 (TAB@.PARENT=savetab) to display TAB2 again, then all the objects are back except the uitabgroup (tabgp2).

Here is the code:

 a=figure(1);

 tabgp = uitabgroup(a);

 tab1 = uitab(tabgp,'Title','Type of Signal');
 tab2 = uitab(tabgp,'Title','Plot Options');

 tabgp2 = uitabgroup(tab2);

 subtab1 = uitab(tabgp2,'Title','Tab1');
 subtab2 = uitab(tabgp2,'Title','Tab2');
 subtab3 = uitab(tabgp2,'Title','Tab3');

 savetab=tab2.Parent;
  end

Then after running this code. I do the following to delete the TAB2 :

 tab2.Parent=[];

and then, if I do :

 tab2.Parent=savetab;

Everything will come back except tabgp2.

I would expect to get everything back, like I usually do with tabs that do not have other Tabs group inside them. The subtab objects are still accessible but not visible eventhough their 'visible' property is set to 'on'.

Is it a Matlab bug or am I doing something wrong ?

Best Regards, Marc