Object can only be in a single Group

[5axes]

Issue with Annotation Plane .. As soon as I try to open a Datum Reference I have this message.

14:43:18 Traceback (most recent call last):
14:43:18 File "C:\Users----\AppData\Roaming\FreeCAD\Mod\GDT.\GDT.py", line 1606, in createObject
14:43:18 makeDatumSystem(datumNAme, obj, None, None)
14:43:18 File "C:\Users----\AppData\Roaming\FreeCAD\Mod\GDT.\GDT.py", line 989, in makeDatumSystem
14:43:18 group.addObject(obj)
14:43:18 RuntimeError: {'sclassname': 'class Base::RuntimeError', 'sErrMsg': 'Object can only be in a single Group', 'sfile': '', 'iline': 0, 'sfunction': '', 'swhat': 'Object can only be in a single Group', 'btranslatable': False, 'breported': False}

[5axes]

I understood a little bit better the origin of the problem but for the moment I can't solve the problem. I cheated by using a try: to avoid having the error but it is still there. From what I could understand between the time when the WB was written and the current version the management of hierarchies has changed and I think that when the author had written his code this kind of problem did not exist. So to be continued