Issue with Partner function in SAP CRM

Hello Experts,

When an user is editing  ACTIVITY and setting status as completed then user name should get display in 'Completed By' partnerfunction 

(As custom code is written in order save badi  that whenever  user will change the status as complete then user name should get display in 'Completed By' partnerfunction). Now for some user it is not happening.

Thanks!!

Prashant