Tag scope are not refreshed

When copying a folder from one Site to another the tags are not getting reindexed.

The list of tags keeps empty even if the new folder contains many files with tags.

On the other hand, if I delete the copied folder in the old site, the tags are not removed.
Even the results (the count behind the tag) aren't resetted.
So if there have been several files with tag resume the tag keeps in the list and even the count.
for example resume(4)

Forum-Post for reference: http://forums.alfresco.com/en/viewtopic.php?f=47&t=20919