On this case the filter was enabled on the assignment task of the Business Suite Connector to capture any change of communication data and update to source back, but that result on adding multiple entry as many as number assignments the user get.
On each time an ABAP role is assigned to the user it also get the existing Function_set and run the BAdi which result in updating the source system back while communication did not change.
Anyway, the requirement is to just to write-back user/email once onlyat creation and those should never change unless it is a correction case;
So a simple resolution is to enable the filter only on create task of ABAP/Business Suite Connector, and disable it on the assignment task.