How to Set-up custom target system in web Manager?

Hi Team,

The One IM version is 8.1.4
we are trying to user web manager and want to manage and edit one of the custom target systems. However it fails in spite of the two method below 

Created a custom AE role and custom permission group

    Assigned the custom permission group to all UNSB forms and tables as well

Assigned a system role to an employee record; assigned all the One identity manager applications roles (administrator roles) to the employee. Still the same error post clicking the 'Change Master' data of UNSAccountB records

The error screen is attached 

    "Unable cast object of type 'VI.WebControls.Edit' to type 'Systems.Windows.Forms.Control'

Best regards,

Prakash