Apache Cayenne ResultIterator and prefetch joint

Question

We are using Cayenne with something like

    ResultIterator<SomeMain> lvSomeMainList = ObjectSelect
                               .query(Anlstamm.class)
                               .and(SomeMain.ORGUNIT_NR.eq(pvOrgUnitNr))
                               .prefetch(SomeMain.RELATION1.joint())
                               .prefetch(SomeMain.RELATION2.joint())
                               .prefetch(SomeMain.RELATION3.joint())
                               .iterator(gvContext);
 

    for (SomeMain bvSomeMain: lvSomeMainList) {

                           bvSomeMain.getMethod_relation1();
                            ...
    }

Cayenne executes the correct joins on DB-Level but instead of fully resolve bvSomeMain, getMethod_relation1 triggers a new select with the already prefetched RELATION1.

We are using Apache Cayenne 4.0

Thanks for a hint.