Dear community,
in the meanwhile I was able to test my scenario also without startoutine, in 7.31 and 7.40
The result is very disappointing!
What has been known since 2013 is still not resolved: http://service.sap.com/sap/support/notes/1145673
That means, even an empty startroutine still causes the problem that DTP filter restrictions with navigational attributes don't work properly!
I'm really wondering why even in the third version (don't believe it worked in 7.30), SAP has not been able to correct this error!!! It is not even solved in BW on HANA...
I will open a new OSS note now.
BR, Martin