Report not working after Release Update 10.2 M020-CPS05 -> CPS10

Hi,

we have the problem that a specific report is not working any more after updating from

10.2 M020-CPS05 to 10.2 M020-CPS10

and

Oracle 11g to Oracle 12c

Java 1.7.0_80-b15 ("Version 7 Update 80") is installed on the client machines.

The report has to do with promotion requests and the source can be found here:

Query Builder Report: getting the related Promotion Requests of a Drawing

If it's needed, I can post the exact report here.

The page is loading continuously for a very very long time. Sometimes it gives out a report, sometimes an error occurs (in German but should give a hint):

Other "smaller" reports work without any delay.

Can anybody confirm this? This is a pretty urgent issue since the report is used by many persons every day.

Thanks!

David