Hi Dirk,
I had raised this concern to SAP support from where we got the solutions. Below is the explanation and solution.
In Table PIQDBAGR_ASSIGNM there should be only one module booking id relation to Appraisal ID relation. But due to some inconsistency, the system was creating two records. One of these records were inconsistent and did not had proper relation, but a line item was created. The line item had module booking Id, extended object but no B506 relation with appraisal ID.
Now while booking students to assessments in "Edit assessment Process" the system picks Module booking id from the above mentioned table and assigns module id as "higher level object". But in our case it is picking the inconsistent record which has a missing relation and is just like a inconsistent line item in the table. Due to this reason higher level object was missing due to which we were not able to grade the student.
Now after deleting that inconsistent record from the table, system picked the correct record and higher level object came back. We were able to grade the student.
Thanks and Regards
Aatish Shukla