From where do the Employee gets assigned in Asset Assignment window for mass addition

Hi Experts,

1. I have few assets where Employee is getting assigned in the back end  but  in front-end assignment window no employee is assigned where those employees are In-Active with which post mass addition gets error out.

2. Please advise from where do this employee is getting populated in back end but where we don't see any employee since it is empty.

3. we null out the EMployee Id in FA Mass Addition table to fix the Issue

Please Advise