Unable to automatically assign via automation

[Krishna Chaitanya]

I am trying to restrict wrong assignment of tickets to users by creating an automation that resets the field of assignee if anyone outside of my group of users tries to change the value. I have achieved this by using this to set user upon the automation trigger:

{{fieldChange.fromString}}

I have attached a screenshot of the error I am getting when trying to do this. It just says Inactive user even though this is an active user of my project and space. Can someone help me with what i need to do differently to avoid this from happening? 

[Randy Michel]

I am having the same issue! I have been trying to resolve it but no dice. I 

[Thanasis Nikolaou]

@Krishna Chaitanya @Randy Michel 
Options are:
1. Try using {{changelog.fromString}} instead of {{fieldChange.fromString}}
2. Set up a backup custom field (Back-up assignee) that stores the assignee by automation every time is set by your group of users. Then create another automation with the "assignee" as a trigger and the condition is that if the initiator of this event IS NOT a member of your group then edit the assignee and copy the value from the "Back-up assignee" field.

[Thanasis Nikolaou]

Hi @Krishna Chaitanya

Is there any particular reason why you chose not to restrict assignee changes in the project permission scheme to that specific group of people? :)