After upgrading ranger from older version to latest : Users in x_user and x_portal_user tables are not in sync and due to this policies populates wrong users after upgrade and service check of plugin components fails.
As part of commit - RangerPolicyRetriever.java [Line No: 253]. Code is to read username using userId. In this function, userId being passed is of x_user table but code written is to read it from x_portal_user.
So when IDs in x_user and x_portal_user are not in sync, this code will return wrong username, and that's why username in policies will be changed with some other username.