I am using Nintex workflow in SP 2016 on premise. An approval workflow uses a Flexi task to send approvals. I have the following Calculated field on the Nintex form of the Flexi Task.

userProfileLookup(Current User, "PreferredName")

Most of the times, the workflow captures the PreferredName of the Last Respondent and display it correctly. But there are times when it returns  #Value! instead. This happens for the same user, as well at different times. 

Any idea of what’s going on. 

Thanks in advance.

Mayank Shyam