Rejoin of a DC Master

We have a little problem with a somewhat older DC Master (UCS 4.1-4 with OX App Suite and Univention AD Connector installed). The local Directory Listener on this master is about 12000000 changes behind, produces 100% CPU load and doesn’t move forward while producing no error messages.
We haven’t had time yet for an in-depth analysis for either the transaction log or the source of the massive amounts of ldap changes (although these might be related to the ad connector configuration).

In order to get the server halfway working again, we thought about the following: instead of getting the server to process all 12 million changes, we force the server to re-join itself. Unfortunately, the univention-join commando won’t work on a DC Master. But can we reach the same result by emptying /usr/lib/univention-install/.index.txt and running univention-run-join-scripts?
Could this work? Or is there a better way?

Best Regards,
Andreas Burkert