Hi Rohit,
Your problem sounds familiar. We have ticket open with SAP since November to fix this issue. Ticket number is 961362.
We are getting in Dump for the program RPCBENUS_ACA_PERSON with duplicate records. This dump is because of the way dependent data maintained on Infotype 21. When a dependent changes type in the middle of month (e.g. From "Domestic Partner" to "Spouse" or "Court Order Dependent" to "Child") system is tyring to create two separate records with same SSN and creating a dump.
In your system try to Identify associate with similiar situation and run this Progrom just for that PERNR and see if you are getting a dump.
Although the table HRBENUS_D_ADDATA also has keys for subty and objps, SAP is not populating them and program is failing.
Class: CL_HRBENUS_ACA_ENGINE
Method: FILL_ADDATA_COVIND