Hi, Samer AL-Sarhan
it is the common problem while running multi-company uses same pos 
while you running pos the session automatically change to closed or any other sate
and your current order will lose.....................
i will send you a module in pos to solve the session problem.........it will check every second your session closed or not and it will display a popup while session close ,
my clients are still using this module in all odoo versions if you have any problem please contact me :9633097060(india) or email me i will send the module to you ,id :manakkunnathjith@gmail.com
py part.....................
class PosConfig(models.Model):
    _inherit = 'pos.config'
    check_session_state_frequency = fields.Integer(
        string="Frequency of Checking the State of the Session",
        default=1, help="The value is set in seconds.")
    @api.model
    def get_status(self, ref):
        lines = self.env['pos.session'].search([('id', '=', ref)])
        result = lines.state
        return result
    @api.model
    def update_status(self, ref):
        code_check = self.env['pos.session'].search([('id', '=', ref)])
        # if code_check == False:
        print 'No postcode in database, writing ....'
        print code_check.state
        code_check.write({'state': 'opened'})
        print code_check.state
        return ref
js part
odoo.define('pos_check_session_state',function(require){
"use strict";
var PopupWidgets = require('point_of_sale.popups');
var gui = require('point_of_sale.gui');
var chrome = require('point_of_sale.chrome');
var PosBaseWidget = require('point_of_sale.BaseWidget');
var popups = require('point_of_sale.popups');
var QWeb = core.qweb;
var _t = core._t;
var PopupWidget = require('point_of_sale.popups');
var _t = core._t;
var ErrorClosedSessionPopupWidget = PopupWidget.extend({
    template:'ErrorClosedSessionPopupWidget',
        init: function(parent, options) {
            var self = this;
            this._super(parent, options);
            self.intervalID = setInterval(function() {
                var order_new = self.pos.pos_session;
                 new Model('pos.config').call('get_status',[order_new.id]).then(function(result){
                    if (result=='opened'){
//                        console.log("opened the session");
                    }
                    else{
                        console.log("session blocked");2
                        self.gui.show_popup('lock1');
                    }
                });
            }, self.pos.config.check_session_state_frequency * 1000);
        },
        show: function(opts) {
            var self = this;
            this._super(opts);
            var order_new = self.pos.pos_session;
            this.$('.cancel').off('click').click(function(){
               new Model('pos.config').call('update_status',[order_new.id]).then(function(result){
                    console.log(result);
                    location.reload();
                });
            });
             this.$('.cancell').off('click').click(function(){
               window.history.back();
               new Model('pos.config').call('update_status',[order_new.id]).then(function(result){
                    console.log(result);
                });
            });
        }
});
gui.define_popup({name:'lock1', widget: ErrorClosedSessionPopupWidget});
chrome.Chrome.include({
//var module = init.PosBaseWidget.extend({
    build_widgets: function(){
        this._super();
            // Add a new Popup 'ErrorClosedSessionPopupWidget'
            this.error_closed_session_popup = new ErrorClosedSessionPopupWidget(this, {});
            this.error_closed_session_popup.appendTo(this.$el);
//            this.screen_selector.popup_set['error-closed-session'] = this.error_closed_session_popup;
            // Hide the popup because all pop up are displayed at the
            // beginning by default
            this.error_closed_session_popup.hide();
    },
});
});
            
Exactly the same problem here. Even the server logs don't show errors or any indication of orders not saved. We are using Firefox on Windows as POS clients, and I don't see any orders stuck in the client localcache.
am on windows using google chrom any one Can help please?