Error on script for customize doctype

i dont know why when i create, supplier name and id tax appear.

But when i save, supplier name and id tax disappear. i wonder where is error on my script

frappe.ui.form.on("IUNI Contract Master Input",{
    refresh:function(frm){
        warm_up_fields(frm)
    },
    party_type:function(frm){
      clear_fields(frm)  
    },
    party_code:function(frm){
        if(frm.doc.party_type=="Supplier"){
			frappe.db.get_value('Supplier', frm.doc.party_code, 'supplier_name', (values) => {
				frm.set_value("supplier_name", values.supplier_name);
			});
			
			frappe.db.get_value('Supplier', frm.doc.party_code, 'tax_id', (values) => {
				frm.set_value("tax_id", values.tax_id);
			});
			
        }
        else if(frm.doc.party_type=="IUNI Employee"){
            frm.set_query('party_code', function() {
			return {
				filters: {
					'status': "Active"
				}
			}
            })
        
			frappe.db.get_value('IUNI Employee', frm.doc.party_code, 'employee_name', (values) => {
				frm.set_value("supplier_name", values.employee_name);
			});
        }
    }
 })
 
 let clear_fields = function(frm){
     frm.set_value("party_code","")
     frm.set_value("supplier_name","")
     frm.set_value("tax_id","")
     
    if(frm.doc.party_type=='Supplier'){
        frm.set_df_property("tax_id", "hidden", 0);
        frm.set_df_property("supplier_name", "hidden", 0);
    }
    else{
        frm.set_df_property("tax_id", "hidden", 1);
        frm.set_df_property("supplier_name", "hidden", 1);
    }
 }
 
 let warm_up_fields = function(frm){
     
     frm.set_value("supplier_name","")
     frm.set_value("tax_id","")
     
    if(frm.doc.party_type=='Supplier'){
        frm.set_df_property("tax_id", "hidden", 0);
        frm.set_df_property("supplier_name", "hidden", 0);
    }
    else{
        frm.set_df_property("tax_id", "hidden", 1);
        frm.set_df_property("supplier_name", "hidden", 1);
    }
 }