I do not understand why 

{#Nautilus. #PackageTreeNautilus} do: [:each | each asClass resetGroups].
or 
GroupManager current "reset" (does not exist) and

followed by

5 timesRepeat:[Smalltalk garbageCollect.].

do not get rid of the registration especially since they are weak

So now what I'm doing instead is

    #AbstractGroup asClass allSubInstances do: [ :each |  SystemAnnouncer uniqueInstance unsubscribe: each ].

And we should probably define that somewhere.

I added a bug entry to not forget.

So now I can continue to unload the refactoring engine, then I will try to reload RB and Nautilus