Hi Moritz,
We can check what activity did CMS perform when the response duration was that long. If you apply parameter –querytiming in to the command line parameter of the CMS server properties along with the path where the log is to be generated
Example:
-querytiming "E:\Anyfoldername\querytiming.log"
(Note : only during non-business hours- as it requires restart of CMS for changes to get effect)
It can give us clue as to why the query went that long, so you can match the time and the activity performed for that duration. You'll have to read the querytiming log, and log file contains information regarding the query, the time the query took to execute, the SI_ID of the user executing the query, and the query string itself.
[This switch use to work in XI 3.1, I am though not sure if this works on BI4.x environment as I haven't got a chance to try this on BI4.x but you can let us know]