BUG: "Users" type field cannot be referenced

BUG: "Users" type field cannot be referenced

Hello, 

It seems "Users" type field sometimes can and other times cannot be referenced.
My app contains a form called  Users, having one field of being type "Users" and named Username

1/ "User" type field cannot be used in list 
The code below create error
UsersList_SelfLookup =  Users[Organization == LoginUser.Organization].distinct( Username);
UsersList_SelfLookup.sort(true);
Trips_Approver:ui.add(UsersList_SelfLookup);

2/ "User" type field can be used while fetching record "On User Input" but not "On success"
The below code works fine "On User Input" but do not  "OnAdd/On success"
input. Username  = FetchedRecord. Username;


Could you please help?
As you probably understood, all for the above is a workaround for the self-lookup that Zoho Creator does not provide. Missing self-lookup creates lots of complications in Apps that do need it to manage employee-manager relationships.

Thanks, 
Adrien