Global site tags not updating correctly

I have global site tags (and post indexer) installed on a budypress multisite.
It seems to have stopped updating.

Easiest demonstration of this is If I look at subsite http://reformgroups.net/oxford/ there is a more complex tag cloud than that shown at http://reformgroups.net/tags/

The extra tags where created recently. Two recently added tags Electoral Reform Society and Unlock Democracy are not show in the group tag cloud. But some other recent additons are showing. In addition two deleted tags (testtag and word test tag) are shown. How can I force a reindex to fix this problem?