workflow permissions are not applied to all users

Hello, 

I have set up a workflow that changes permissions when a contract is changed to Active Status. 

According to this, whoever is listed in the property Internal Supplier Contract will receive edit rights. 

In this object, I have three users listed as contacts, but M-Files is only granting edit rights to one of the users.

Why is this happening?  How can it be fixed.

Regards, 

Irene