<menuitem id="menu_contacts_doctors"
          name="Nurses"
          parent="menu_contacts"
          action="contacts.action_contacts"
          sequence="1"/>   //Action Working Correctly

<menuitem id="menu_contacts_patients"
          name="Patients"
          parent="menu_contacts"
          action="action_patients_tree"
          sequence="0"/> //Action not working correctly, after assigning action in it, it disable menuitem, tree view is defined below

xml version="1.0"?>
<odoo>
    <data>
        <record id="action_patients_tree" model="ir.actions.act_window">
            <field name="name">Patientsfield>
            <field name="res_model">medical.patientsfield>
            <field name="view_mode">tree,formfield>
        record>
        <record model="ir.ui.view" id="medical_patients_view_tree">
            <field name="name">Patientsfield>
            <field name="model">medical.patientsfield>
            <field name="arch" type="xml">
                <tree>
                    <field name="name">field>
                    <field name="diagnosis">field>
                    <field name="passport_number">field>
                tree>
            field>
        record>
    data>
odoo>