Workitem reaching a wrong agent for release of PO

[kavitha mahishi]

Hi,

A workflow is implemented for release of Purchase Order(BUS2012).
  For some PO's, due to some strange reason...PO meant for the role B1
are going to A1. The agents(userid's) for sending emails of B1,A1,C1,etc are
mentioned in a custom table. Also the release strategy's are mapped in
the OMGS transaction.
   I tried debugging the method, but could not reach any solution.

  The recipients are established by accessing a custom table
ZMM_PO_AUTH. Standard Role(MM_po_rel) with function module
('ME_REL_GET_RESPONSIBLE') is used. User exit 'EXIT_SAPLEBNF_001' is
implemented to read the agents (userid's) from this table.
These agents are determined by the purchasing groups of the Purchase
Order and Release code. The different Release codes are A1, B1,
C1,D1,E1. Further the Release codes are determined by the Release
strategy while creating the PO. Different Release strategy's  are A1,
B1, C1, D1(which have nothing to do with the Release Codes A1,
B1,...). These Release strategy's are picked up by the system based on
the Po amount which is all mentioned in the transaction OMGS.

Also another important observation is that is is not happening always
but only sometimes when the release strategy on the PO is changed.
Also it does not happen everytime a release strategy is changed, which
is making it impossible to replicate the case.

Please help me resolve this.

Thanks,
kavitha